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Toufik Zebbiche - One of the best experts on this subject based on the ideXlab platform.

  • Stagnation Temperature effect on the supersonic flow around pointed airfoils with application for air
    Mechanics & Industry, 2018
    Co-Authors: Rahima Takhnouni, Toufik Zebbiche, Abderrazak Allali
    Abstract:

    The aim of this work is to develop a new numerical calculation program to determine the effect of the Stagnation Temperature on the calculation of the supersonic flow around a pointed airfoils using the equations for oblique shock wave and the Prandtl Meyer expansion, under the model at high Temperature, calorically imperfect and thermally perfect gas, lower than the dissociation threshold of the molecules. The specific heat at constant pressure does not remain constant and varies with the Temperature. The new model allows making corrections to the perfect gas model designed for low Stagnation Temperature, low Mach number, low incidence angle and low airfoil thickness. The Stagnation Temperature is an important parameter in our model. The airfoil should be pointed at the leading edge to allow an attached shock solution to be seen. The airfoil is discretized into several panels on the extrados and the intrados, placed one adjacent to the other. The distribution of the flow on the panel in question gives a compression or an expansion according to the deviation of the flow with respect to the old adjacent panel. The program determines all the aerodynamic characteristics of the flow and in particular the aerodynamic coefficients. The calculation accuracy depends on the number of panels considered on the airfoil. The application is made for high values of Stagnation Temperature, Mach number and airfoil thickness. A comparison between our high Temperature model and the perfect gas model is presented, in order to determine an application limit of the latter. The application is for air.

  • Stagnation Temperature effect on the conical shock with application for air
    Chinese Journal of Aeronautics, 2018
    Co-Authors: Toufik Elaichi, Toufik Zebbiche
    Abstract:

    Abstract The aim of this work is to realize a new numerical program based on the development of a mathematical model allowing determining the parameters of the supersonic flow through a conical shock under hypothesis at high Temperature, in the context of correcting the perfect gas model. In this case, the specific heat at constant pressure does not remain constant and varies with the increase of Temperature. The Stagnation Temperature becomes an important parameter in the calculation. The mathematical model is presented by the numerical resolution of a system of first-order nonlinear differential equations with three coupled unknowns for initial conditions. The numerical resolution is made by adapting the higher order Runge Kutta method. The parameters through the conical shock can be determined by considering a new model of an oblique shock at high Temperature. All isentropic parameters of after the shock flow depend on the deviation of the flow from the transverse direction. The comparison of the results is done with the perfect gas model for low Stagnation Temperatures, upstream Mach number and cone deviation angle. A calculation of the error is made between our high Temperature model and the perfect gas model. The application is made for air.

  • Stagnation Temperature effect on the conical shock with application for air
    Elsevier, 2018
    Co-Authors: Toufik Elaichi, Toufik Zebbiche
    Abstract:

    The aim of this work is to realize a new numerical program based on the development of a mathematical model allowing determining the parameters of the supersonic flow through a conical shock under hypothesis at high Temperature, in the context of correcting the perfect gas model. In this case, the specific heat at constant pressure does not remain constant and varies with the increase of Temperature. The Stagnation Temperature becomes an important parameter in the calculation. The mathematical model is presented by the numerical resolution of a system of first-order nonlinear differential equations with three coupled unknowns for initial conditions. The numerical resolution is made by adapting the higher order Runge Kutta method. The parameters through the conical shock can be determined by considering a new model of an oblique shock at high Temperature. All isentropic parameters of after the shock flow depend on the deviation of the flow from the transverse direction. The comparison of the results is done with the perfect gas model for low Stagnation Temperatures, upstream Mach number and cone deviation angle. A calculation of the error is made between our high Temperature model and the perfect gas model. The application is made for air. Keywords: Calorically imperfect gas, Conical shock, High Temperature, Numerical integration, Oblique shock, Perfect gas model, Runge Kutta method, Supersonic flo

  • Effect of Stagnation Temperature on the supersonic axisymmetric minimum length nozzle conception with application for air
    Thermophysics and Aeromechanics, 2011
    Co-Authors: Toufik Zebbiche
    Abstract:

    When the Stagnation Temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this Temperature. The gas remains perfect; its state equation remains always valid, except, it is named in more by calorically imperfect gas. The aim of this work is to trace the profiles of the supersonic axisymmetric Minimum Length Nozzle to have a uniform and parallel flow at the exit section, when the Stagnation Temperature is taken into account, lower than the dissociation threshold of the molecules, and to have for each exit Mach number and Stagnation Temperature shape of nozzle. The method of characteristics is used with the algorithm of the second order finite differences method. The form of the nozzle has a point of deflection and an initial angle of expansion. The comparison is made with the calorically perfect gas. The application is for air.

  • Stagnation Temperature effect on the supersonic axisymmetric minimum length nozzle design with application for air
    Advances in Space Research, 2011
    Co-Authors: Toufik Zebbiche
    Abstract:

    Abstract When the Stagnation Temperature of a perfect gas increases, the specific heats and their ratio do not remain constant any more and start to vary with this Temperature. The gas remains perfect; its state equation remains always valid, except, it is named in more by calorically imperfect gas. The aim of this work is to trace the profiles of the supersonic axisymmetric minimum length nozzle to have a uniform and parallel flow at the exit section, when the Stagnation Temperature is taken into account, lower than the dissociation threshold of the molecules, and to have for each exit Mach number and Stagnation Temperature shape of nozzle. The method of characteristics is used with the algorithm of the second order finite differences method. The form of the nozzle has a point of deflection and an initial angle of expansion. The comparison is made with the calorically perfect gas.

A. N. Shiplyuk - One of the best experts on this subject based on the ideXlab platform.

David R. Buttsworth - One of the best experts on this subject based on the ideXlab platform.

  • Stagnation Temperature in a cold hypersonic flow produced by a light free piston compression facility
    Experiments in Fluids, 2013
    Co-Authors: Agung Widodo, David R. Buttsworth
    Abstract:

    Stagnation Temperatures at the nozzle exit of the University of Southern Queensland hypersonic wind tunnel facility have been identified using an aspirating tube device with a 0.075 mm diameter k-type butt-welded thermocouple junction positioned at its inlet. Because of the finite thermal inertia of the thermocouple, a response time correction is introduced, and uncertainties in the response time correction are assessed and minimized by operating the aspirating device over a range of different initial Temperatures. Pressure measurements within the barrel of the wind tunnel facility were used to estimate a theoretical upper bound on the flow Stagnation Temperature by assuming isentropic compression of the test gas. Results demonstrate that for the current operating conditions, the gas which is first delivered into the hypersonic nozzle has a Stagnation Temperature almost identical to the isentropic compression value of around 560 K, but a cooling effect is registered for the duration of the test flow which is about 200 ms. Thermodynamic simulations based on an unsteady energy balance model with turbulent heat transfer from the test gas within the barrel demonstrate a cooling effect of a similar magnitude to that indicated by the measured Temperature variation, suggesting that strong mixing of the test gas occurs within the barrel during flow discharge through the hypersonic nozzle.

  • Stagnation Temperature measurements in the USQ hypersonic wind tunnel
    2010
    Co-Authors: Agung Sugeng Widodo, David R. Buttsworth
    Abstract:

    A thermocouple probe with a heated shield has been used to measure Stagnation Temperature at the nozzle exit of the University of Southern Queensland hypersonic wind tunnel. The thermocouple probe consisted of a welded junction T-type thermocouple mounted within a heated tube with a vent hole downstream of the junction. Pressure transducers within the barrel of the wind tunnel have also been used to obtain the pressure history during the free piston compression process. The pressure measurements have been used to provide a theoretical value for the flow Stagnation Temperature for direct comparison with the thermocouple measurements. Assuming isentropic compression of the test gas, the flow Stagnation Temperature would be about 571 K for the current operating condition. After applying a response-time correction for the thermocouple signals, a Stagnation Temperature value of about 495 K was obtained from the measurements. The measured Stagnation Temperature of the test gas is somewhat lower than the isentropic value because of heat loss from the test gas to the barrel during the test gas compression and discharge process.

  • Transient Temperature probe measurements in a Mach 4 nitrogen jet
    Experiments in Fluids, 2004
    Co-Authors: David R. Buttsworth, Terry V. Jones
    Abstract:

    Stagnation Temperature measurements have been obtained in a Mach 4 free jet of nitrogen using a technique based on transient thin film heat flux probe measurements. The uncertainty in the Stagnation Temperature measurements depends on the probe location within the jet but is typically around ±5 K at the centre of the jet. The thin film heat flux probe technique also provides a measurement of the heat transfer coefficient of the thin film probes with an uncertainty of around ±4% at the centre of the jet. Pitot pressure measurements were also obtained within the jet. Analysis of the heat transfer coefficient results yields the Mach number and velocity profiles which are compared with results from the pitot probe measurements. Jet velocities identified using the thin film probe and the pitot probe techniques produce results with uncertainties of less than ±2% at the centre of the jet. Measurements of RMS Stagnation Temperature fluctuations indicate values of around 3 K at the centre of the jet to more than 10 K in the shear layer.

  • High bandwidth Stagnation Temperature measurements in a Mach 6 gun tunnel flow
    Experimental Thermal and Fluid Science, 2003
    Co-Authors: David R. Buttsworth, Terry V. Jones
    Abstract:

    Abstract Temperature is an important parameter in most high speed flow experiments, but it is sometimes a difficult parameter to measure, particularly in short-duration facilities. Stagnation Temperature measurements have been obtained using transient thin film heat flux probes in a Mach 6 carbon dioxide flow produced by the Oxford University Gun Tunnel. The probes were operated over a range of surface Temperatures so that the flow Stagnation Temperature could be identified independently of the convective heat transfer coefficient of the probes. The time-averaged measurements indicate a significant drop in Stagnation Temperature with time and this implies that significant cooling of the test gas occurred within the barrel during the compression process and/or during the flow discharge process. During the last 12 ms of flow, the time-averaged Stagnation Temperature indicated by the probe was 610±10 K for the present operating conditions. During the same 12 ms flow period, the probe measurements also indicate Stagnation Temperature fluctuations of about 2.3 K (rms) for frequencies between 1 and 25 kHz. Based on pitot pressure fluctuation measurements at essentially the same location within the nozzle, it is concluded that the measured Temperature fluctuations are primarily due to fluctuations in entropy. Entropy fluctuations within the Mach 6 flow probably arise because of the turbulent heat transfer to the barrel.

S. M. Frolov - One of the best experts on this subject based on the ideXlab platform.

Terry V. Jones - One of the best experts on this subject based on the ideXlab platform.

  • Transient Temperature probe measurements in a Mach 4 nitrogen jet
    Experiments in Fluids, 2004
    Co-Authors: David R. Buttsworth, Terry V. Jones
    Abstract:

    Stagnation Temperature measurements have been obtained in a Mach 4 free jet of nitrogen using a technique based on transient thin film heat flux probe measurements. The uncertainty in the Stagnation Temperature measurements depends on the probe location within the jet but is typically around ±5 K at the centre of the jet. The thin film heat flux probe technique also provides a measurement of the heat transfer coefficient of the thin film probes with an uncertainty of around ±4% at the centre of the jet. Pitot pressure measurements were also obtained within the jet. Analysis of the heat transfer coefficient results yields the Mach number and velocity profiles which are compared with results from the pitot probe measurements. Jet velocities identified using the thin film probe and the pitot probe techniques produce results with uncertainties of less than ±2% at the centre of the jet. Measurements of RMS Stagnation Temperature fluctuations indicate values of around 3 K at the centre of the jet to more than 10 K in the shear layer.

  • High bandwidth Stagnation Temperature measurements in a Mach 6 gun tunnel flow
    Experimental Thermal and Fluid Science, 2003
    Co-Authors: David R. Buttsworth, Terry V. Jones
    Abstract:

    Abstract Temperature is an important parameter in most high speed flow experiments, but it is sometimes a difficult parameter to measure, particularly in short-duration facilities. Stagnation Temperature measurements have been obtained using transient thin film heat flux probes in a Mach 6 carbon dioxide flow produced by the Oxford University Gun Tunnel. The probes were operated over a range of surface Temperatures so that the flow Stagnation Temperature could be identified independently of the convective heat transfer coefficient of the probes. The time-averaged measurements indicate a significant drop in Stagnation Temperature with time and this implies that significant cooling of the test gas occurred within the barrel during the compression process and/or during the flow discharge process. During the last 12 ms of flow, the time-averaged Stagnation Temperature indicated by the probe was 610±10 K for the present operating conditions. During the same 12 ms flow period, the probe measurements also indicate Stagnation Temperature fluctuations of about 2.3 K (rms) for frequencies between 1 and 25 kHz. Based on pitot pressure fluctuation measurements at essentially the same location within the nozzle, it is concluded that the measured Temperature fluctuations are primarily due to fluctuations in entropy. Entropy fluctuations within the Mach 6 flow probably arise because of the turbulent heat transfer to the barrel.