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V. Mani

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Papers by V. Mani

A Proposed Method for Generating Tabulated Data for Wall Interference Correction in Unsteady Subsonic Wind Tunnel Testing

In the current research, the results of some wind tunnel experiments on a moving airfoil with plu... more In the current research, the results of some wind tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted walls. In both cases, pressure coefficients of different points on the upper surface of the airfoil have been measured during the plunging oscillation. The difference between the outputs is considered as the wall effect. The mentioned difference is extracted and regulated as a function of some non-dimensional parameters to provide a database for correction of the results of experiments on oscillating airfoils conducted in conventional wind tunnels. The correction is only considered for points located in the front portion of the airfoil to make sure there is no flow separation in that region. Finally, numerical experiments are employed to show the performance of the method.

Unsteady Surface Pressure Measurement on a Pitching Air Foil

An experimental analysis of the unsteady pressure distribution on a two dimensional pitching Eppl... more

Wake analysis of a plunging airfoil

An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveye... more An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveyed with a Hot-wire rake containing seven I-wires. The aim of these measurements was to study the velocity profiles behind the oscillating airfoil trailing edge. Influences of reduced frequency and angle of attack were studied in details. It was shown that the angle of attack and reduced frequency are the most important parameters which influence on the velocity profiles. The momentum deficit was relative to reduced frequency and amplitude of oscillation and its behaviours were changed after static stall angles. At the angle of attack beyond static stall angle flow separation causes increasing the momentum deficit. The velocity profile has approximately symmetric shape profile. Data were taken at mean incidence angles of 0, 8 degrees at reduced frequencies of 0.09 to 0.56. The nondimensional amplitude of oscillation was 0.27. The corresponding Reynolds numbers, based on the chord length, were 25000 and 150000. NOMENCLATURE

Drag reduction of 3D bluff body using SDBD plasma actuators

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, Oct 8, 2020

The paper examines how is it possible for an incumbent political party to stay in power for long ... more The paper examines how is it possible for an incumbent political party to stay in power for long periods of time without having to trade-off rents for holding office. It presents a new way of explaining and measuring the real effects of rent-extraction on political re-election in local government. It models local government due to the different and exact way rent-extraction can be measured there; through pork-barrel spending on public goods upon which a political party is able to extract rents. Setting rents as an endogenous variable permits the model to evaluate their effect on political re-election and preservation of power. The paper alters certain typical assumptions of other political agency models in order to test its effects in a more realistic scenario of politics. The incumbent's decision on rents and public good production directly affects the state of the economy upon which the voters decide whether to re-elect the incumbent or not. Incumbents make their decisions based on observing the economic growth shock. In a repeated game setting an incumbent will always chose the optimal strategy with respect to the observed growth shock. This way, for high enough levels of economic growth an incumbent party may stay in office for an infinite amount of periods and keep maximizing rents with respect to the given constraints, without having to trade-off rents for holding office. The paper presents empirical evidence on United States gubernatorial and state legislature elections from 1992 to 2008 to evaluate the underlining theory.

Experimental investigation into the flow structure of plasma induced Jet in a 2-D Cross-Flow

European Journal of Mechanics B-fluids, Mar 1, 2023

Experimental investigation of vortex shedding of an airfoil at post-stall incidences

Proceedings Of The Institution Of Mechanical Engineers, Part G: Journal Of Aerospace Engineering, Jul 11, 2022

The harmonic vortex shedding from airfoil happens in various incidences. It has noticeable effect... more The harmonic vortex shedding from airfoil happens in various incidences. It has noticeable effects on the structure design and aerodynamic performance. In this paper, wind tunnel tests were conducted on a stationary NACA4412 airfoil at angles of attack ranging from [Formula: see text] to [Formula: see text] and Re number between [Formula: see text] and [Formula: see text] to examine the vortex shedding frequency and Strouhal number. The wake dynamics at post-stall incidences were investigated by surface pressure, wake flow velocity measurement, and smoke flow visualization. Three phases of the wake dynamics were observed with increasing the incidences beyond the stall: (i) the tiny vortices are shed from the airfoil’s suction side with scattered frequencies, (ii) the shear layer is separated from the LE, rolls up over the airfoil’s suction side and forms the harmonic vortex street, and (iii) the separation point moves from the airfoil’s suction side to the pressure side and leads to the vortex shedding like the bluff bodies. Frequency analysis of aerodynamic loads shows that the flow field’s low-frequency feature has a substantial effect normal to the surface while the vortex street unsteadiness impacts both perpendicular and parallel to the surface. The base pressure coefficient increases suddenly by the vortex street onset in the region (ii) and reaches about 0.4. The universal Strouhal number of 0.18 that is independent of Reynolds number was captured for the angles of attack well beyond the stall. Flow visualization shows that the vortex street establishes longitudinally closer to the airfoil at lower freestream velocity compared to the upper one.

Wall-Interference Correction for the Surface-Pressure Hysteresis of an Airfoil Undergoing Plunging Motion

Transactions of The Canadian Society for Mechanical Engineering, Jun 1, 2015

In the current research, the results of a number of wind-tunnel experiments on a moving airfoil w... more In the current research, the results of a number of wind-tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted test-section walls to provide resemblance to a far-field condition. The difference in results obtained from two test-section configurations can be considered as the wall effect and regulated as a function of non-dimensional parameters which can be further used for correcting experimental results obtained from conventional wind tunnels. When the derived correction factor is applied to a numerical simulation of a wind tunnel with a conventional test section (for points located in the front portion of the airfoil), the resulting pressure variations closely resembled that of a far-field numerical simulation. This methodology showed promising results for the specific configurations used in this research.

Улучшение подъемных характеристик крыла со сверхкритическим профилем при использовании модулированного импульсного струйного актуатора

Pisʹma v Žurnal tehničeskoj fiziki, 2022

В результате экспериментального исследования предложена импульсная система управления потоком на ... more В результате экспериментального исследования предложена импульсная система управления потоком на устройство увеличения подъемной силы крыла с несущей поверхностью модели NASA SC(2)-0714 в диапазоне чисел Рейнольдса, соответствующих фазам взлета и приземления. Применен инновационный метод модуляции сигнала, обеспечивающий возможность одновременного использования достоинств как низких, так и высоких частот возбуждения в одном управляющем сигнале актуатора, которые считаются эффективными при управлении срывом потока. Обнаружено, что благодаря применению модулированных импульсных струй можно увеличивать коэффициенты подъемной силы и лобового сопротивления по сравнению с соответствующими значениями для простой импульсной струи. Ключевые слова: управление потоком, конфигурация с высокой подъемной силой, импульсная струя, импульсная модуляция, аэродинамическая эффективность.

Aerodynamic Characteristics of Conventional and Innovative High Lift Swept Wings

Journal of Bionic Engineering, May 1, 2019

The new bird inspired wing sweep was introduced and compared with straight and conventional swept... more The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds' wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0˚ to 24˚ angles of attack and Reynolds numbers of 4.3×10 4 , 8.6×10 4 , 1.3×10 5 , and 1.7×10 5. Wind tunnel test results show that wings with an innovative sweep at α > 0 have more lift for Reynolds numbers between 4.3×10 4 and 8.6×10 4. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24˚ for Reynolds between 1.3×10 5 and 1.7×10 5. An increase in lift and having sufficient aerodynamic performance in low Reynolds numbers for birds' inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps.

Улучшение подъемных характеристик крыла со сверхкритическим профилем при использовании модулированного импульсного струйного актуатора

Письма в журнал технической физики

In this experimental investigation, a pulse flow control system on a high-lift device of a wing w... more In this experimental investigation, a pulse flow control system on a high-lift device of a wing with a NASA SC(2)-0714 airfoil within the Reynolds number range of the take-off and landing phases, is proposed. In this study, an innovative method of signal modulation has been used in order to simultaneously exploit the benefits of both low and high excitation frequencies in one actuator driving signal that are known to be effective in separation control. It is observed that the lift and drag coefficients are improved due to the use of modulated pulse jets compared to the simple pulse jet.

The Effect of Single Dielectric Barrier Discharge Actuators in Reducing Drag on an Ahmed Body

Fluids, 2020

The feasibility of a single dielectric barrier discharge (SDBD) actuator in controlling flow over... more The feasibility of a single dielectric barrier discharge (SDBD) actuator in controlling flow over an Ahmed body, representing a simplified car model, has been numerically and experimentally investigated at Reynolds numbers of 7.68×105 and 2.25×105. The Ahmed body had slant angles of 25∘ and 35∘. The results showed that SDBD actuators could significantly enhance the aerodynamic performance of the Ahmed body. Several arrangements of the actuators on the slant surface and the rear face of the model were examined to identify the most effective arrangement for drag reduction. This arrangement resulted in an approximately 6.1% drag reduction. This improvement in aerodynamic performance is attributed to the alteration of three-dimensional wake structures due to the presence of SDBD, which coincides with surface pressure variations on the slant and rear faces of the Ahmed body.

Effect Of Amplitude And Mean Angle Of Attack On Wake Of An Oscillating Airfoil

The unsteady wake of an EPPLER 361 airfoil in pitching motion has been investigated in a subsonic... more The unsteady wake of an EPPLER 361 airfoil in pitching motion has been investigated in a subsonic wind tunnel by hot-wire anemometry. The airfoil was given the pitching motion about the one-quarter chord axis at reduced frequency of 0182. Streamwise mean velocity profiles (wake profiles) were investigated at several vertically aligned points behind the airfoil at one-quarter chord downstream distance from trailing edge. Oscillation amplitude and mean angle of attack were varied to determine the effects on wake profiles. When the maximum dynamic angle of attack was below the static stall angle of attack, weak effects on wake were found by increasing oscillation amplitude and mean angle of attack. But, for higher angles of attack strong unsteady effects were appeared on the wake.

Wake analysis of a plunging airfoil

An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveye... more An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveyed with a Hot-wire rake containing seven I-wires. The aim of these measurements was to study the velocity profiles behind the oscillating airfoil trailing edge. Influences of reduced frequency and angle of attack were studied in details. It was shown that the angle of attack and reduced frequency are the most important parameters which influence on the velocity profiles. The momentum deficit was relative to reduced frequency and amplitude of oscillation and its behaviours were changed after static stall angles. At the angle of attack beyond static stall angle flow separation causes increasing the momentum deficit. The velocity profile has approximately symmetric shape profile. Data were taken at mean incidence angles of 0, 8 degrees at reduced frequencies of 0.09 to 0.56. The nondimensional amplitude of oscillation was 0.27. The corresponding Reynolds numbers, based on the chord length, w...

A Proposed Method for Generating Tabulated Data for Wall Interference Correction in Unsteady Subsonic Wind Tunnel Testing

In the current research, the results of some wind tunnel experiments on a moving airfoil with plu... more In the current research, the results of some wind tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted walls. In both cases, pressure coefficients of different points on the upper surface of the airfoil have been measured during the plunging oscillation. The difference between the outputs is considered as the wall effect. The mentioned difference is extracted and regulated as a function of some non-dimensional parameters to provide a data-base for correction of the results of experiments on oscillating airfoils conducted in conventional wind tunnels. The correction is only considered for points located in the front portion of the airfoil to make sure there is no flow separation in that region. Finally, numerical experiments are employed to show the performance of the method.

Drag reduction of 3D bluff body using SDBD plasma actuators

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2020

In the current research, a series of different combinations of plasma SDBD actuators mounted on a... more In the current research, a series of different combinations of plasma SDBD actuators mounted on a simplified road vehicle have been experimentally studied to find the optimum position of the actuators for controlling the flow separation and reducing the vehicle form drag. Separation point of the flow over the rear ramp, large trailing vortices of the standard model, and laminar separation bubble (LSB) of the rear ramp leading edge are among the most significant factors to be controlled. The experiments were conducted at Reynolds numbers ranging from 0.55 × 106 to 1.11 × 106 in a subsonic wind tunnel while the pressure distribution over the model and its streamwise force balance were accurately measured. Significant drag reduction due to the use of DBD actuators was observed. As such, for the range of tested Reynolds numbers, a maximum of 25.1% of drag reduction in the vehicle drag coefficient could be achieved. The optimum combinations of activation voltages (6, 9, and 12 kV) and wa...

Wall-Interference Correction for the Surface-Pressure Hysteresis of an Airfoil Undergoing Plunging Motion

Transactions of the Canadian Society for Mechanical Engineering, 2015

In the current research, the results of a number of wind-tunnel experiments on a moving airfoil w... more In the current research, the results of a number of wind-tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted test-section walls to provide resemblance to a far-field condition. The difference in results obtained from two test-section configurations can be considered as the wall effect and regulated as a function of non-dimensional parameters which can be further used for correcting experimental results obtained from conventional wind tunnels. When the derived correction factor is applied to a numerical simulation of a wind tunnel with a conventional test section (for points located in the front portion of the airfoil), the resulting pressure variations closely resembled that of a far-field numerical simulation. This methodology showed promising results for the specific configurations used in this research.

Aerodynamic Characteristics of Conventional and Innovative High Lift Swept Wings

Journal of Bionic Engineering, 2019

The new bird inspired wing sweep was introduced and compared with straight and conventional swept... more The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds' wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0˚ to 24˚ angles of attack and Reynolds numbers of 4.3×10 4 , 8.6×10 4 , 1.3×10 5 , and 1.7×10 5. Wind tunnel test results show that wings with an innovative sweep at α > 0 have more lift for Reynolds numbers between 4.3×10 4 and 8.6×10 4. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24˚ for Reynolds between 1.3×10 5 and 1.7×10 5. An increase in lift and having sufficient aerodynamic performance in low Reynolds numbers for birds' inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps.

Experimental and Numerical Study of the Unsteady Wake of a Supercritical Airfoil in a Compressible Flow

Journal of Aerospace Technology and Management, 2018

Sliding Mode Active Vibration Control and Three Axis Attitude Control using Four Reaction Wheels

International Journal of Computer Applications, 2016

The most important problems in satellites are their energy supply and decreasing weight. One of t... more The most important problems in satellites are their energy supply and decreasing weight. One of the solutions is using flexible appendages. Flexibility can supply both energy and weight loss in satellites. Also other appendages like antennas and mechanical arms can be flexible. But flexibility can produce some vibrations. These vibrations cause complexity attitude control systems due to flexible appendages.

Experimental and numerical analysis of aerodynamic effects of repair patches on damaged airfoils

Journal of Mechanical Science and Technology, 2017

This investigation assesses the change of aerodynamic characteristics of triangular and star-shap... more This investigation assesses the change of aerodynamic characteristics of triangular and star-shaped damaged airfoils with repair patches. Both experimental and numerical methods to determine aerodynamic coefficients are used in this study. The test model is a NACA 64 1-412 airfoil full span, which is considered by using five schematics: Clean model, damaged model, upper repaired model, lower repaired model, and fully repaired model. Repair patches are chosen based on the Aircraft battle damage repair (ABDR) manuals. Various effects of repair schemes on triangular and star-shaped damages are quantitatively and qualitatively illustrated. A novel visualization method by paint and oil is used in wind tunnel tests to study the effects of repair patches on the damaged airfoil.

A Proposed Method for Generating Tabulated Data for Wall Interference Correction in Unsteady Subsonic Wind Tunnel Testing

In the current research, the results of some wind tunnel experiments on a moving airfoil with plu... more In the current research, the results of some wind tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted walls. In both cases, pressure coefficients of different points on the upper surface of the airfoil have been measured during the plunging oscillation. The difference between the outputs is considered as the wall effect. The mentioned difference is extracted and regulated as a function of some non-dimensional parameters to provide a database for correction of the results of experiments on oscillating airfoils conducted in conventional wind tunnels. The correction is only considered for points located in the front portion of the airfoil to make sure there is no flow separation in that region. Finally, numerical experiments are employed to show the performance of the method.

Unsteady Surface Pressure Measurement on a Pitching Air Foil

An experimental analysis of the unsteady pressure distribution on a two dimensional pitching Eppl... more

Wake analysis of a plunging airfoil

An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveye... more An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveyed with a Hot-wire rake containing seven I-wires. The aim of these measurements was to study the velocity profiles behind the oscillating airfoil trailing edge. Influences of reduced frequency and angle of attack were studied in details. It was shown that the angle of attack and reduced frequency are the most important parameters which influence on the velocity profiles. The momentum deficit was relative to reduced frequency and amplitude of oscillation and its behaviours were changed after static stall angles. At the angle of attack beyond static stall angle flow separation causes increasing the momentum deficit. The velocity profile has approximately symmetric shape profile. Data were taken at mean incidence angles of 0, 8 degrees at reduced frequencies of 0.09 to 0.56. The nondimensional amplitude of oscillation was 0.27. The corresponding Reynolds numbers, based on the chord length, were 25000 and 150000. NOMENCLATURE

Drag reduction of 3D bluff body using SDBD plasma actuators

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, Oct 8, 2020

The paper examines how is it possible for an incumbent political party to stay in power for long ... more The paper examines how is it possible for an incumbent political party to stay in power for long periods of time without having to trade-off rents for holding office. It presents a new way of explaining and measuring the real effects of rent-extraction on political re-election in local government. It models local government due to the different and exact way rent-extraction can be measured there; through pork-barrel spending on public goods upon which a political party is able to extract rents. Setting rents as an endogenous variable permits the model to evaluate their effect on political re-election and preservation of power. The paper alters certain typical assumptions of other political agency models in order to test its effects in a more realistic scenario of politics. The incumbent's decision on rents and public good production directly affects the state of the economy upon which the voters decide whether to re-elect the incumbent or not. Incumbents make their decisions based on observing the economic growth shock. In a repeated game setting an incumbent will always chose the optimal strategy with respect to the observed growth shock. This way, for high enough levels of economic growth an incumbent party may stay in office for an infinite amount of periods and keep maximizing rents with respect to the given constraints, without having to trade-off rents for holding office. The paper presents empirical evidence on United States gubernatorial and state legislature elections from 1992 to 2008 to evaluate the underlining theory.

Experimental investigation into the flow structure of plasma induced Jet in a 2-D Cross-Flow

European Journal of Mechanics B-fluids, Mar 1, 2023

Experimental investigation of vortex shedding of an airfoil at post-stall incidences

Proceedings Of The Institution Of Mechanical Engineers, Part G: Journal Of Aerospace Engineering, Jul 11, 2022

The harmonic vortex shedding from airfoil happens in various incidences. It has noticeable effect... more The harmonic vortex shedding from airfoil happens in various incidences. It has noticeable effects on the structure design and aerodynamic performance. In this paper, wind tunnel tests were conducted on a stationary NACA4412 airfoil at angles of attack ranging from [Formula: see text] to [Formula: see text] and Re number between [Formula: see text] and [Formula: see text] to examine the vortex shedding frequency and Strouhal number. The wake dynamics at post-stall incidences were investigated by surface pressure, wake flow velocity measurement, and smoke flow visualization. Three phases of the wake dynamics were observed with increasing the incidences beyond the stall: (i) the tiny vortices are shed from the airfoil’s suction side with scattered frequencies, (ii) the shear layer is separated from the LE, rolls up over the airfoil’s suction side and forms the harmonic vortex street, and (iii) the separation point moves from the airfoil’s suction side to the pressure side and leads to the vortex shedding like the bluff bodies. Frequency analysis of aerodynamic loads shows that the flow field’s low-frequency feature has a substantial effect normal to the surface while the vortex street unsteadiness impacts both perpendicular and parallel to the surface. The base pressure coefficient increases suddenly by the vortex street onset in the region (ii) and reaches about 0.4. The universal Strouhal number of 0.18 that is independent of Reynolds number was captured for the angles of attack well beyond the stall. Flow visualization shows that the vortex street establishes longitudinally closer to the airfoil at lower freestream velocity compared to the upper one.

Wall-Interference Correction for the Surface-Pressure Hysteresis of an Airfoil Undergoing Plunging Motion

Transactions of The Canadian Society for Mechanical Engineering, Jun 1, 2015

In the current research, the results of a number of wind-tunnel experiments on a moving airfoil w... more In the current research, the results of a number of wind-tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted test-section walls to provide resemblance to a far-field condition. The difference in results obtained from two test-section configurations can be considered as the wall effect and regulated as a function of non-dimensional parameters which can be further used for correcting experimental results obtained from conventional wind tunnels. When the derived correction factor is applied to a numerical simulation of a wind tunnel with a conventional test section (for points located in the front portion of the airfoil), the resulting pressure variations closely resembled that of a far-field numerical simulation. This methodology showed promising results for the specific configurations used in this research.

Улучшение подъемных характеристик крыла со сверхкритическим профилем при использовании модулированного импульсного струйного актуатора

Pisʹma v Žurnal tehničeskoj fiziki, 2022

В результате экспериментального исследования предложена импульсная система управления потоком на ... more В результате экспериментального исследования предложена импульсная система управления потоком на устройство увеличения подъемной силы крыла с несущей поверхностью модели NASA SC(2)-0714 в диапазоне чисел Рейнольдса, соответствующих фазам взлета и приземления. Применен инновационный метод модуляции сигнала, обеспечивающий возможность одновременного использования достоинств как низких, так и высоких частот возбуждения в одном управляющем сигнале актуатора, которые считаются эффективными при управлении срывом потока. Обнаружено, что благодаря применению модулированных импульсных струй можно увеличивать коэффициенты подъемной силы и лобового сопротивления по сравнению с соответствующими значениями для простой импульсной струи. Ключевые слова: управление потоком, конфигурация с высокой подъемной силой, импульсная струя, импульсная модуляция, аэродинамическая эффективность.

Aerodynamic Characteristics of Conventional and Innovative High Lift Swept Wings

Journal of Bionic Engineering, May 1, 2019

The new bird inspired wing sweep was introduced and compared with straight and conventional swept... more The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds' wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0˚ to 24˚ angles of attack and Reynolds numbers of 4.3×10 4 , 8.6×10 4 , 1.3×10 5 , and 1.7×10 5. Wind tunnel test results show that wings with an innovative sweep at α > 0 have more lift for Reynolds numbers between 4.3×10 4 and 8.6×10 4. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24˚ for Reynolds between 1.3×10 5 and 1.7×10 5. An increase in lift and having sufficient aerodynamic performance in low Reynolds numbers for birds' inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps.

Улучшение подъемных характеристик крыла со сверхкритическим профилем при использовании модулированного импульсного струйного актуатора

Письма в журнал технической физики

In this experimental investigation, a pulse flow control system on a high-lift device of a wing w... more In this experimental investigation, a pulse flow control system on a high-lift device of a wing with a NASA SC(2)-0714 airfoil within the Reynolds number range of the take-off and landing phases, is proposed. In this study, an innovative method of signal modulation has been used in order to simultaneously exploit the benefits of both low and high excitation frequencies in one actuator driving signal that are known to be effective in separation control. It is observed that the lift and drag coefficients are improved due to the use of modulated pulse jets compared to the simple pulse jet.

The Effect of Single Dielectric Barrier Discharge Actuators in Reducing Drag on an Ahmed Body

Fluids, 2020

The feasibility of a single dielectric barrier discharge (SDBD) actuator in controlling flow over... more The feasibility of a single dielectric barrier discharge (SDBD) actuator in controlling flow over an Ahmed body, representing a simplified car model, has been numerically and experimentally investigated at Reynolds numbers of 7.68×105 and 2.25×105. The Ahmed body had slant angles of 25∘ and 35∘. The results showed that SDBD actuators could significantly enhance the aerodynamic performance of the Ahmed body. Several arrangements of the actuators on the slant surface and the rear face of the model were examined to identify the most effective arrangement for drag reduction. This arrangement resulted in an approximately 6.1% drag reduction. This improvement in aerodynamic performance is attributed to the alteration of three-dimensional wake structures due to the presence of SDBD, which coincides with surface pressure variations on the slant and rear faces of the Ahmed body.

Effect Of Amplitude And Mean Angle Of Attack On Wake Of An Oscillating Airfoil

The unsteady wake of an EPPLER 361 airfoil in pitching motion has been investigated in a subsonic... more The unsteady wake of an EPPLER 361 airfoil in pitching motion has been investigated in a subsonic wind tunnel by hot-wire anemometry. The airfoil was given the pitching motion about the one-quarter chord axis at reduced frequency of 0182. Streamwise mean velocity profiles (wake profiles) were investigated at several vertically aligned points behind the airfoil at one-quarter chord downstream distance from trailing edge. Oscillation amplitude and mean angle of attack were varied to determine the effects on wake profiles. When the maximum dynamic angle of attack was below the static stall angle of attack, weak effects on wake were found by increasing oscillation amplitude and mean angle of attack. But, for higher angles of attack strong unsteady effects were appeared on the wake.

Wake analysis of a plunging airfoil

An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveye... more An experimental measurements of unsteady wakes behind a sinusoidally plunging airfoil was surveyed with a Hot-wire rake containing seven I-wires. The aim of these measurements was to study the velocity profiles behind the oscillating airfoil trailing edge. Influences of reduced frequency and angle of attack were studied in details. It was shown that the angle of attack and reduced frequency are the most important parameters which influence on the velocity profiles. The momentum deficit was relative to reduced frequency and amplitude of oscillation and its behaviours were changed after static stall angles. At the angle of attack beyond static stall angle flow separation causes increasing the momentum deficit. The velocity profile has approximately symmetric shape profile. Data were taken at mean incidence angles of 0, 8 degrees at reduced frequencies of 0.09 to 0.56. The nondimensional amplitude of oscillation was 0.27. The corresponding Reynolds numbers, based on the chord length, w...

A Proposed Method for Generating Tabulated Data for Wall Interference Correction in Unsteady Subsonic Wind Tunnel Testing

In the current research, the results of some wind tunnel experiments on a moving airfoil with plu... more In the current research, the results of some wind tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted walls. In both cases, pressure coefficients of different points on the upper surface of the airfoil have been measured during the plunging oscillation. The difference between the outputs is considered as the wall effect. The mentioned difference is extracted and regulated as a function of some non-dimensional parameters to provide a data-base for correction of the results of experiments on oscillating airfoils conducted in conventional wind tunnels. The correction is only considered for points located in the front portion of the airfoil to make sure there is no flow separation in that region. Finally, numerical experiments are employed to show the performance of the method.

Drag reduction of 3D bluff body using SDBD plasma actuators

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2020

In the current research, a series of different combinations of plasma SDBD actuators mounted on a... more In the current research, a series of different combinations of plasma SDBD actuators mounted on a simplified road vehicle have been experimentally studied to find the optimum position of the actuators for controlling the flow separation and reducing the vehicle form drag. Separation point of the flow over the rear ramp, large trailing vortices of the standard model, and laminar separation bubble (LSB) of the rear ramp leading edge are among the most significant factors to be controlled. The experiments were conducted at Reynolds numbers ranging from 0.55 × 106 to 1.11 × 106 in a subsonic wind tunnel while the pressure distribution over the model and its streamwise force balance were accurately measured. Significant drag reduction due to the use of DBD actuators was observed. As such, for the range of tested Reynolds numbers, a maximum of 25.1% of drag reduction in the vehicle drag coefficient could be achieved. The optimum combinations of activation voltages (6, 9, and 12 kV) and wa...

Wall-Interference Correction for the Surface-Pressure Hysteresis of an Airfoil Undergoing Plunging Motion

Transactions of the Canadian Society for Mechanical Engineering, 2015

In the current research, the results of a number of wind-tunnel experiments on a moving airfoil w... more In the current research, the results of a number of wind-tunnel experiments on a moving airfoil with plunging motion are presented. The experiments have been conducted in two different configurations which are tunnels with conventional and slotted test-section walls to provide resemblance to a far-field condition. The difference in results obtained from two test-section configurations can be considered as the wall effect and regulated as a function of non-dimensional parameters which can be further used for correcting experimental results obtained from conventional wind tunnels. When the derived correction factor is applied to a numerical simulation of a wind tunnel with a conventional test section (for points located in the front portion of the airfoil), the resulting pressure variations closely resembled that of a far-field numerical simulation. This methodology showed promising results for the specific configurations used in this research.

Aerodynamic Characteristics of Conventional and Innovative High Lift Swept Wings

Journal of Bionic Engineering, 2019

The new bird inspired wing sweep was introduced and compared with straight and conventional swept... more The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds' wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0˚ to 24˚ angles of attack and Reynolds numbers of 4.3×10 4 , 8.6×10 4 , 1.3×10 5 , and 1.7×10 5. Wind tunnel test results show that wings with an innovative sweep at α > 0 have more lift for Reynolds numbers between 4.3×10 4 and 8.6×10 4. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24˚ for Reynolds between 1.3×10 5 and 1.7×10 5. An increase in lift and having sufficient aerodynamic performance in low Reynolds numbers for birds' inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps.

Experimental and Numerical Study of the Unsteady Wake of a Supercritical Airfoil in a Compressible Flow

Journal of Aerospace Technology and Management, 2018

Sliding Mode Active Vibration Control and Three Axis Attitude Control using Four Reaction Wheels

International Journal of Computer Applications, 2016

The most important problems in satellites are their energy supply and decreasing weight. One of t... more The most important problems in satellites are their energy supply and decreasing weight. One of the solutions is using flexible appendages. Flexibility can supply both energy and weight loss in satellites. Also other appendages like antennas and mechanical arms can be flexible. But flexibility can produce some vibrations. These vibrations cause complexity attitude control systems due to flexible appendages.

Experimental and numerical analysis of aerodynamic effects of repair patches on damaged airfoils

Journal of Mechanical Science and Technology, 2017

This investigation assesses the change of aerodynamic characteristics of triangular and star-shap... more This investigation assesses the change of aerodynamic characteristics of triangular and star-shaped damaged airfoils with repair patches. Both experimental and numerical methods to determine aerodynamic coefficients are used in this study. The test model is a NACA 64 1-412 airfoil full span, which is considered by using five schematics: Clean model, damaged model, upper repaired model, lower repaired model, and fully repaired model. Repair patches are chosen based on the Aircraft battle damage repair (ABDR) manuals. Various effects of repair schemes on triangular and star-shaped damages are quantitatively and qualitatively illustrated. A novel visualization method by paint and oil is used in wind tunnel tests to study the effects of repair patches on the damaged airfoil.