ICIASF '95 Record. International Congress on Instrumentation in Aerospace Simulation Facilities
ABSTRACT The work presented is a comparison between the performances of simple miniature hot-wire... more ABSTRACT The work presented is a comparison between the performances of simple miniature hot-wire gauges and commercially available surface hot-films for measuring surface skin friction on wind tunnel models under laminar and turbulent flow conditions. It is shown that the wire gauge is the more sensitive device in terms of response to the flow whilst, at the same time, being the more robust of the two gauges. In addition, the roughness effects due to the 25 μm thick polymer substrate reduce the film gauge sensor response
The flows over cavities are of interest in many different areas of engineering from thermal equip... more The flows over cavities are of interest in many different areas of engineering from thermal equipment to engines and machinery and can be found in landinggear wells, surface-mounted instrumentation on aircraft, cut-outs on marine vehicles, printed circuit boards and land vehicles. The very nature of these flows can cause large changes in pressure, velocity, and density fluctuations as well as generate strong propagating acoustic waves. These are typical cavity applications where reductions in pressure fluctuation levels, heat transfer, vibration, noise, and structural fatigue are still of considerable interest. This experimental study was undertaken to examine the effect of cavity length on flow oscillations produced by an open cavity placed within a subsonic turbulent boundary layer. A narrow rectangular cavity with a constant width-to-depth ratio was immersed within such a boundary layer. Microphone-type pressure transducers were used to record the pressure time histories for six ...
Safety protocols on both military and commercial aircraft rely on knowledge of fire dynamics, tem... more Safety protocols on both military and commercial aircraft rely on knowledge of fire dynamics, temperature distributions and thermal mass transfer of specific chemical components. Indeed, the temperature field associated within an incendiary flash has numerous implications, particularly in the aircraft survivability arena. Present knowledge is limited when it comes to determining the local; temperature field around a burning incendiary and although there are full-scale experimental facilities these are often too expensive to perform all the parameters that are necessary to understand this type of event. Furthermore, if a fire has been initiated due to the instigation of a short duration pyrotechnic event then the scenario is further complicated, and is even more so if the event is in close proximity to a pool of fuel. Indeed, the ignition of a fuel pool by an incendiary device, such as a armour-piercing incendiary (API), has not been exhaustively covered, and it is widely accepted th...
Steel catenary risers (SCRs) are an enabling technology for deepwater oil and gas production. Too... more Steel catenary risers (SCRs) are an enabling technology for deepwater oil and gas production. Tools to analyse and design SCRs are available which show that the point where the riser first touches the soil, termed the touchdown point (TDP) is critical. However our understanding of fluid/riser/soil interaction is limited, hence the oil and gas industry has concerns regarding the levels of conservatism in SCR design, and margins of safety. The purpose of this study is to examine the interaction between a pipe (representing a section of the SCR), a clay seabed, and the surrounding seawater. This paper documents some of the results and observations from the full scale harbour test riser experiments which examined the 3D effect of fluid/riser/soil interaction around the TDP. The riser, a 110m (360-ft) long 0.1683m (6-5/8 inch) diameter pipe, was draped from an actuator on the harbour wall to an anchor point on the seabed. The top end of the pipe string was actuated using a programmable l...
The paper describes the arrangements by which it is possible to operate a wide variety of wind tu... more The paper describes the arrangements by which it is possible to operate a wide variety of wind tunnel instrumentation using a single desk-top microcomputer. Various types of instrumentation are introduced and illustration is given of how they are interfaced with the microcomputer.
In this paper some results from a wind tunnel study of a circular jet issuing normally into a cro... more In this paper some results from a wind tunnel study of a circular jet issuing normally into a crossflow are reported. The experimental apparatus which has recently been developed, allowing large areas of the interaction region to be surveyed, is described and the preliminary findings discussed. The data obtained will be of use in the future enhancement of potential flow models for predicting jet interference phenomena.
ABSTRACT In this paper the appraisal of a folding dome structure under the influence of wind load... more ABSTRACT In this paper the appraisal of a folding dome structure under the influence of wind loading is discussed. The foldable structure considered is constructed from an assembly of interconnected elements, together with a flexible membrane, all of which are initially store in a compact form and on deployment expand, like an umbrella, into a dome structure. Loading on the dome was obtained from a wind tunnel analysis of the pressure distribution over the roof of a 1:10 scale model of the structure. The critical loading obtained from the wind tunnel investigation was used, together with individual member and material tests, to form a series of numerical non-linear finite element models which were, in turn, used to investigate the forces within the structure. The numerical analysis was used to determine the critical wind loading that the structure can sustain, as well as providing a method by which to investigate the failure modes of the structure. In order to enhance the load carrying capacity of the dome it was found that both the strength and stiffness of the structural nodes needed to be enhanced and in addition, changes were necessary to substantially increase the stiffness of the individual member and caps.
Forced convection around the human head 1. The parameters determining the forced convective heat ... more Forced convection around the human head 1. The parameters determining the forced convective heat loss from a heated body in an air stream are outlined. 2. Local forced convective heat transfer distributions around the human head and a heated vertical cylinder at various wind speeds in a climatic chamber have been found to be similar and related to the aerodynamic flow patterns. 3. From the local convective coefficient distribution, values for the overall convective coefficient hN at various wind speeds have been evaluated. These are seen to agree closely with existing whole body coefficients determined by other methods.
Journal of Physics E: Scientific Instruments, 1973
A small surface plate calorimeter, about 8 mm*12 mm*0.2 mm thick, is described for measuring the ... more A small surface plate calorimeter, about 8 mm*12 mm*0.2 mm thick, is described for measuring the steady state convection and radiation heat transfer from the surface of a heated body in air. The calorimeter, which may be attached to the surface of the body with double-sided adhesive tape, has been tested on heated cylinders in free and forced convection.
When the liquid in a tank undergoes sudden movement, as in the case of a fuel tank in an aircraft... more When the liquid in a tank undergoes sudden movement, as in the case of a fuel tank in an aircraft or in a marine vessel, it may be subjected to as many as 6 degrees of freedom. Three of these are in rotation; yaw, pitch and roll, and three in translation; sway, surge, and heave. Work is currently being conducted on simulating the effects of the liquid motion under roll conditions in a rectangular tank of dimensions 1.9 x 0.94 x 1.2 m 3 located on a 6 degree of freedom simulator capable of mimicking the movements typical of an aircrafts performance. At present, water is being used to investigate the fluid motion when subjected to oscillating roll frequency of 0.35 Hz and oscillation amplitudes of 2.42 0 , 3.50 0 , and 4.71 0 for different liquid depths. It has been found that under such motions, typical of those obtained within the flight envelope of military, private and commercial aircraft, a dynamic hydraulic jump can occur. This jump is out of phase with the roll motion and is produced as the fluid abruptly changes direction within the tank. As the tank reaches its lowest rotational position in the roll manoeuvre the fluid level at this point of the tank increases rapidly against the end wall causing splashing, resulting in bubble formation and a fine spray. This change in direction increases the fluid depth and this has to move against the residual oncoming fluid that is at a much lower depth, resulting in a very dynamic, moving, wave that breaks and forms into a hydraulic jump comprised of air and liquid mixing. This preliminary investigation into the characterization of this phenomenon using water shows that the spatial characteristics of the hydraulic jump and the dynamic range of the resultant spray are affected by the amplitude of the tank oscillation.
Engineering Turbulence Modelling and Experiments, 1993
In this paper a comparison is made between two flow visualisation techniques, namely smoke in air... more In this paper a comparison is made between two flow visualisation techniques, namely smoke in air and laser induced fluorescence (LIF) in water, both utilising quantitative digital image processing. The flow fields investigated are those of a single axi-symmetric circular jet issuing into still fluid and two similar jets issuing into still fluid but then impinging upon one another at a short distance from the nozzle exits. Data are presented for overall profile shapes, in terms of pixel intensities, as well as overall widths and growth rates in the downstream direction. In most cases these compare favourably with data obtained using conventional anemometry techniques. An enhanced experimental arrangement which is currently being utilised to investigate the time-dependent aspects of the twin impining jet flows is also discussed.
Natural convection around the human head 1. Factors determining the convective flow patterns arou... more Natural convection around the human head 1. Factors determining the convective flow patterns around the human head in 'still' conditions are discussed in relation to body posture. 2. These flow patterns have been visualized using a schlieren optical system which reveals that the head has a thicker 'insulating' layer of convecting air in the erect posture than in the supine position. 3. Local convective and radiative heat transfer measurements from the head have been made using surface calorimeters. These results are seen to be closely related to the thickness of the convective boundary layer flows. 4. The total convective and radiative heat loss from the head of a subject in the erect and supine position has been evaluated from the local measurements. For the head of the supine subject the heat loss was found to be 30% more than when the subject was standing.
Surface shear stress measurement is of fundamental importance in aerodynamics for studying lamina... more Surface shear stress measurement is of fundamental importance in aerodynamics for studying laminar to turbulent transition, surface vortical structures, drag determination and is a necessary diagnostic requirement for not only large aerodynamic surfaces but also for rotodynamic machinery. Currently, there are many methods for determining the shear stress at the surface ranging from velocity profiles to heated elements and small surface obstacles, but all of them rely upon point measurement of the shear stress value. The advantage of having a methodology to determine the full-field shear stress is, therefore, of immense value to the aerodynamic community. It is this particular area that is to be addressed by reporting the work carried out to determine the use of liquid crystals for shear stress measurements at high Mach number.
Past research suggests that droplets and liquid/air mixing may enhance the flammability limits of... more Past research suggests that droplets and liquid/air mixing may enhance the flammability limits of the fuel within a tank. However, the liquid dynamics have yet to be characterized under even the simplest of aircraft maneuvers. To improve our understanding of this hazard an experimental investigation of liquid dynamics of water in a rectangular tank experiencing aircraft dynamics was undertaken using a state-of-the art motion simulator to examined low frequency, low amplitude roll oscillations. A high-speed imaging system was used to capture the event and two major flow phenomena were captured; a hydraulic jump and wave interactions. The former poses a significant vulnerability hazard due to droplet separation and enhanced liquid/air mixing and may create localized regions of flammable fuel/oxygen mixtures in an otherwise inerted tank, whereas the latter produces droplet separation through interaction and may behave as secondary ignition sources that are self-sustaining. An investiga...
This paper describes the preliminary development of a new form of the standard pulsed wire anemom... more This paper describes the preliminary development of a new form of the standard pulsed wire anemometer, and details the initial results obtained from it. The new instrument described here differs from the pulsed wire anemometer in that the probe consists of only two wires, a sensor wire and a pulsed wire, thus creating a simpler and more compact probe with an inherently better yaw response compared to the three wire design. New electronic hardware has been designed to control the probe, which includes a relay switching circuit, which alternates the roles of the two probe wires, thus allowing the flow direction to be unambiguously defined with only two wires. The instrument is best used under program control, as part of an on-line data acquisition system.
A wind-tunnel study has been conducted of the near-wake region associated with large-eddy breakup... more A wind-tunnel study has been conducted of the near-wake region associated with large-eddy breakup (LEBU) surface drag-reduction devices, using a novel method for the video analysis of smoke-flow LEBU visualizations in conjunction with hot-wire anemometry and Preston-tube measurements in the wakes of two tandem LEBUS. The turbulence intensity profiles associated with the undisturbed boundary layers and the LEBU modified flows are presented, together with Preston tube test results illustrating the variation in skin friction coefficient just downstream of the LEBUs.
ICIASF '95 Record. International Congress on Instrumentation in Aerospace Simulation Facilities
ABSTRACT The work presented is a comparison between the performances of simple miniature hot-wire... more ABSTRACT The work presented is a comparison between the performances of simple miniature hot-wire gauges and commercially available surface hot-films for measuring surface skin friction on wind tunnel models under laminar and turbulent flow conditions. It is shown that the wire gauge is the more sensitive device in terms of response to the flow whilst, at the same time, being the more robust of the two gauges. In addition, the roughness effects due to the 25 μm thick polymer substrate reduce the film gauge sensor response
The flows over cavities are of interest in many different areas of engineering from thermal equip... more The flows over cavities are of interest in many different areas of engineering from thermal equipment to engines and machinery and can be found in landinggear wells, surface-mounted instrumentation on aircraft, cut-outs on marine vehicles, printed circuit boards and land vehicles. The very nature of these flows can cause large changes in pressure, velocity, and density fluctuations as well as generate strong propagating acoustic waves. These are typical cavity applications where reductions in pressure fluctuation levels, heat transfer, vibration, noise, and structural fatigue are still of considerable interest. This experimental study was undertaken to examine the effect of cavity length on flow oscillations produced by an open cavity placed within a subsonic turbulent boundary layer. A narrow rectangular cavity with a constant width-to-depth ratio was immersed within such a boundary layer. Microphone-type pressure transducers were used to record the pressure time histories for six ...
Safety protocols on both military and commercial aircraft rely on knowledge of fire dynamics, tem... more Safety protocols on both military and commercial aircraft rely on knowledge of fire dynamics, temperature distributions and thermal mass transfer of specific chemical components. Indeed, the temperature field associated within an incendiary flash has numerous implications, particularly in the aircraft survivability arena. Present knowledge is limited when it comes to determining the local; temperature field around a burning incendiary and although there are full-scale experimental facilities these are often too expensive to perform all the parameters that are necessary to understand this type of event. Furthermore, if a fire has been initiated due to the instigation of a short duration pyrotechnic event then the scenario is further complicated, and is even more so if the event is in close proximity to a pool of fuel. Indeed, the ignition of a fuel pool by an incendiary device, such as a armour-piercing incendiary (API), has not been exhaustively covered, and it is widely accepted th...
Steel catenary risers (SCRs) are an enabling technology for deepwater oil and gas production. Too... more Steel catenary risers (SCRs) are an enabling technology for deepwater oil and gas production. Tools to analyse and design SCRs are available which show that the point where the riser first touches the soil, termed the touchdown point (TDP) is critical. However our understanding of fluid/riser/soil interaction is limited, hence the oil and gas industry has concerns regarding the levels of conservatism in SCR design, and margins of safety. The purpose of this study is to examine the interaction between a pipe (representing a section of the SCR), a clay seabed, and the surrounding seawater. This paper documents some of the results and observations from the full scale harbour test riser experiments which examined the 3D effect of fluid/riser/soil interaction around the TDP. The riser, a 110m (360-ft) long 0.1683m (6-5/8 inch) diameter pipe, was draped from an actuator on the harbour wall to an anchor point on the seabed. The top end of the pipe string was actuated using a programmable l...
The paper describes the arrangements by which it is possible to operate a wide variety of wind tu... more The paper describes the arrangements by which it is possible to operate a wide variety of wind tunnel instrumentation using a single desk-top microcomputer. Various types of instrumentation are introduced and illustration is given of how they are interfaced with the microcomputer.
In this paper some results from a wind tunnel study of a circular jet issuing normally into a cro... more In this paper some results from a wind tunnel study of a circular jet issuing normally into a crossflow are reported. The experimental apparatus which has recently been developed, allowing large areas of the interaction region to be surveyed, is described and the preliminary findings discussed. The data obtained will be of use in the future enhancement of potential flow models for predicting jet interference phenomena.
ABSTRACT In this paper the appraisal of a folding dome structure under the influence of wind load... more ABSTRACT In this paper the appraisal of a folding dome structure under the influence of wind loading is discussed. The foldable structure considered is constructed from an assembly of interconnected elements, together with a flexible membrane, all of which are initially store in a compact form and on deployment expand, like an umbrella, into a dome structure. Loading on the dome was obtained from a wind tunnel analysis of the pressure distribution over the roof of a 1:10 scale model of the structure. The critical loading obtained from the wind tunnel investigation was used, together with individual member and material tests, to form a series of numerical non-linear finite element models which were, in turn, used to investigate the forces within the structure. The numerical analysis was used to determine the critical wind loading that the structure can sustain, as well as providing a method by which to investigate the failure modes of the structure. In order to enhance the load carrying capacity of the dome it was found that both the strength and stiffness of the structural nodes needed to be enhanced and in addition, changes were necessary to substantially increase the stiffness of the individual member and caps.
Forced convection around the human head 1. The parameters determining the forced convective heat ... more Forced convection around the human head 1. The parameters determining the forced convective heat loss from a heated body in an air stream are outlined. 2. Local forced convective heat transfer distributions around the human head and a heated vertical cylinder at various wind speeds in a climatic chamber have been found to be similar and related to the aerodynamic flow patterns. 3. From the local convective coefficient distribution, values for the overall convective coefficient hN at various wind speeds have been evaluated. These are seen to agree closely with existing whole body coefficients determined by other methods.
Journal of Physics E: Scientific Instruments, 1973
A small surface plate calorimeter, about 8 mm*12 mm*0.2 mm thick, is described for measuring the ... more A small surface plate calorimeter, about 8 mm*12 mm*0.2 mm thick, is described for measuring the steady state convection and radiation heat transfer from the surface of a heated body in air. The calorimeter, which may be attached to the surface of the body with double-sided adhesive tape, has been tested on heated cylinders in free and forced convection.
When the liquid in a tank undergoes sudden movement, as in the case of a fuel tank in an aircraft... more When the liquid in a tank undergoes sudden movement, as in the case of a fuel tank in an aircraft or in a marine vessel, it may be subjected to as many as 6 degrees of freedom. Three of these are in rotation; yaw, pitch and roll, and three in translation; sway, surge, and heave. Work is currently being conducted on simulating the effects of the liquid motion under roll conditions in a rectangular tank of dimensions 1.9 x 0.94 x 1.2 m 3 located on a 6 degree of freedom simulator capable of mimicking the movements typical of an aircrafts performance. At present, water is being used to investigate the fluid motion when subjected to oscillating roll frequency of 0.35 Hz and oscillation amplitudes of 2.42 0 , 3.50 0 , and 4.71 0 for different liquid depths. It has been found that under such motions, typical of those obtained within the flight envelope of military, private and commercial aircraft, a dynamic hydraulic jump can occur. This jump is out of phase with the roll motion and is produced as the fluid abruptly changes direction within the tank. As the tank reaches its lowest rotational position in the roll manoeuvre the fluid level at this point of the tank increases rapidly against the end wall causing splashing, resulting in bubble formation and a fine spray. This change in direction increases the fluid depth and this has to move against the residual oncoming fluid that is at a much lower depth, resulting in a very dynamic, moving, wave that breaks and forms into a hydraulic jump comprised of air and liquid mixing. This preliminary investigation into the characterization of this phenomenon using water shows that the spatial characteristics of the hydraulic jump and the dynamic range of the resultant spray are affected by the amplitude of the tank oscillation.
Engineering Turbulence Modelling and Experiments, 1993
In this paper a comparison is made between two flow visualisation techniques, namely smoke in air... more In this paper a comparison is made between two flow visualisation techniques, namely smoke in air and laser induced fluorescence (LIF) in water, both utilising quantitative digital image processing. The flow fields investigated are those of a single axi-symmetric circular jet issuing into still fluid and two similar jets issuing into still fluid but then impinging upon one another at a short distance from the nozzle exits. Data are presented for overall profile shapes, in terms of pixel intensities, as well as overall widths and growth rates in the downstream direction. In most cases these compare favourably with data obtained using conventional anemometry techniques. An enhanced experimental arrangement which is currently being utilised to investigate the time-dependent aspects of the twin impining jet flows is also discussed.
Natural convection around the human head 1. Factors determining the convective flow patterns arou... more Natural convection around the human head 1. Factors determining the convective flow patterns around the human head in 'still' conditions are discussed in relation to body posture. 2. These flow patterns have been visualized using a schlieren optical system which reveals that the head has a thicker 'insulating' layer of convecting air in the erect posture than in the supine position. 3. Local convective and radiative heat transfer measurements from the head have been made using surface calorimeters. These results are seen to be closely related to the thickness of the convective boundary layer flows. 4. The total convective and radiative heat loss from the head of a subject in the erect and supine position has been evaluated from the local measurements. For the head of the supine subject the heat loss was found to be 30% more than when the subject was standing.
Surface shear stress measurement is of fundamental importance in aerodynamics for studying lamina... more Surface shear stress measurement is of fundamental importance in aerodynamics for studying laminar to turbulent transition, surface vortical structures, drag determination and is a necessary diagnostic requirement for not only large aerodynamic surfaces but also for rotodynamic machinery. Currently, there are many methods for determining the shear stress at the surface ranging from velocity profiles to heated elements and small surface obstacles, but all of them rely upon point measurement of the shear stress value. The advantage of having a methodology to determine the full-field shear stress is, therefore, of immense value to the aerodynamic community. It is this particular area that is to be addressed by reporting the work carried out to determine the use of liquid crystals for shear stress measurements at high Mach number.
Past research suggests that droplets and liquid/air mixing may enhance the flammability limits of... more Past research suggests that droplets and liquid/air mixing may enhance the flammability limits of the fuel within a tank. However, the liquid dynamics have yet to be characterized under even the simplest of aircraft maneuvers. To improve our understanding of this hazard an experimental investigation of liquid dynamics of water in a rectangular tank experiencing aircraft dynamics was undertaken using a state-of-the art motion simulator to examined low frequency, low amplitude roll oscillations. A high-speed imaging system was used to capture the event and two major flow phenomena were captured; a hydraulic jump and wave interactions. The former poses a significant vulnerability hazard due to droplet separation and enhanced liquid/air mixing and may create localized regions of flammable fuel/oxygen mixtures in an otherwise inerted tank, whereas the latter produces droplet separation through interaction and may behave as secondary ignition sources that are self-sustaining. An investiga...
This paper describes the preliminary development of a new form of the standard pulsed wire anemom... more This paper describes the preliminary development of a new form of the standard pulsed wire anemometer, and details the initial results obtained from it. The new instrument described here differs from the pulsed wire anemometer in that the probe consists of only two wires, a sensor wire and a pulsed wire, thus creating a simpler and more compact probe with an inherently better yaw response compared to the three wire design. New electronic hardware has been designed to control the probe, which includes a relay switching circuit, which alternates the roles of the two probe wires, thus allowing the flow direction to be unambiguously defined with only two wires. The instrument is best used under program control, as part of an on-line data acquisition system.
A wind-tunnel study has been conducted of the near-wake region associated with large-eddy breakup... more A wind-tunnel study has been conducted of the near-wake region associated with large-eddy breakup (LEBU) surface drag-reduction devices, using a novel method for the video analysis of smoke-flow LEBU visualizations in conjunction with hot-wire anemometry and Preston-tube measurements in the wakes of two tandem LEBUS. The turbulence intensity profiles associated with the undisturbed boundary layers and the LEBU modified flows are presented, together with Preston tube test results illustrating the variation in skin friction coefficient just downstream of the LEBUs.
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Papers by Norman Toy