Gas Dynamics MCQs Aeronautical Engineering)

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The fundamental equation of gas dynamics is the: a) Bernoulli equation b) Navier-Stokes equation c) Euler equation d) Reynolds equation Answer: c) Euler equation In gas dynamics, the “stagnation pressure” is defined as: a) The pressure at a point in a compressible flow b) The pressure measured when the flow is brought to rest adiabatically c) The pressure at the nozzle throat d) The pressure difference between two points in the flow Answer: b) The pressure measured when the flow is brought to rest adiabatically For a compressible flow, the “Mach number” is defined as: a) The ratio of the flow velocity to the speed of sound in the fluid b) The ratio of static pressure to dynamic pressure c) The ratio of temperature to pressure d) The ratio of density to viscosity Answer: a) The ratio of the flow velocity to the speed of sound in the fluid The “isentropic” process is characterized by: a) No heat transfer and no change in entropy b) Constant pressure and constant temperature c) Constant entropy and no work done d) Constant temperature and volume Answer: a) No heat transfer and no change in entropy The “normal shock wave” is a type of shock wave that: a) Is perpendicular to the flow direction b) Forms at an angle to the flow direction c) Occurs when the flow is subsonic d) Does not affect the flow properties Answer: a) Is perpendicular to the flow direction The “Prandtl-Meyer expansion” is used to describe: a) Flow acceleration in supersonic flow b) Flow deceleration in subsonic flow c) Shock wave propagation in compressible flow d) Boundary layer behavior in turbulent flow Answer: a) Flow acceleration in supersonic flow The “Rayleigh flow” is characterized by: a) Isentropic expansion and compression b) Constant temperature and variable pressure c) Heat addition or removal with a change in velocity d) Constant pressure and variable temperature Answer: c) Heat addition or removal with a change in velocity The “Mach number” of the flow at the nozzle exit is often used to determine: a) The efficiency of the nozzle b) The static temperature c) The shock wave strength d) The flow velocity Answer: a) The efficiency of the nozzle In the “Fanno flow,” the characteristic feature is: a) Frictional effects with constant total pressure b) Heat addition with constant velocity c) Isentropic flow with variable temperature d) Expansion in supersonic flow with variable pressure Answer: a) Frictional effects with constant total pressure The “isentropic” flow process assumes: a) No heat transfer and no change in entropy b) Constant temperature and pressure c) Steady flow with constant velocity d) Adiabatic and reversible flow conditions Answer: d) Adiabatic and reversible flow conditions The “compressibility factor” is used to account for: a) The deviation of a real gas from ideal gas behavior b) The variation of pressure with temperature c) The effect of temperature on viscosity d) The influence of density on thermal conductivity Answer: a) The deviation of a real gas from ideal gas behavior The “conservation of mass” in gas dynamics is expressed by the: a) Continuity equation b) Momentum equation c) Energy equation d) Navier-Stokes equation Answer: a) Continuity equation The “Mach number” of 1 indicates: a) The flow is at sonic speed b) The flow is at subsonic speed c) The flow is at supersonic speed d) The flow is at hypersonic speed Answer: a) The flow is at sonic speed In a converging-diverging nozzle, the “choking” condition occurs when: a) The flow velocity at the nozzle throat equals the speed of sound b) The flow pressure is zero at the nozzle exit c) The temperature is constant throughout the nozzle d) The flow velocity is constant at the nozzle exit Answer: a) The flow velocity at the nozzle throat equals the speed of sound The “area-Mach number relationship” is used to: a) Determine the flow speed in a compressible flow b) Calculate the drag coefficient of an airfoil c) Predict the lift force on an aircraft d) Measure the boundary layer thickness Answer: a) Determine the flow speed in a compressible flow The “Joukowski transform” is used to: a) Transform the flow field around an airfoil into a simpler form b) Calculate the lift coefficient of a wing c) Analyze the flow separation over a cylindrical body d) Predict the shock wave pattern around a supersonic aircraft Answer: a) Transform the flow field around an airfoil into a simpler form The “thrust coefficient” is used to: a) Measure the efficiency of a jet engine or nozzle b) Calculate the drag force on an aircraft c) Determine the lift-to-drag ratio of an airfoil d) Predict the compressibility effects in high-speed flows Answer: a) Measure the efficiency of a jet engine or nozzle The “critical Mach number” is the Mach number at which: a) The first signs of shock waves appear b) The aircraft reaches maximum lift c) The drag coefficient is minimized d) The flow speed is maximized Answer: a) The first signs of shock waves appear In “subsonic” flow through a nozzle, the flow velocity: a) Increases as the cross-sectional area decreases b) Decreases as the cross-sectional area decreases c) Remains constant throughout the nozzle d) Increases with increasing temperature Answer: a) Increases as the cross-sectional area decreases The “Tsiolkovsky rocket equation” relates: a) The change in velocity of a rocket to the exhaust velocity and mass flow rate b) The pressure drop across a nozzle to the flow velocity c) The temperature change in a gas to its specific heat capacity d) The lift force on an airfoil to its angle of attack Answer: a) The change in velocity of a rocket to the exhaust velocity and mass flow rate In “compressible flow,” the “Bernoulli equation” is modified to account for: a) The changes in density and temperature b) The changes in pressure and velocity c) The changes in viscosity and turbulence d) The changes in altitude and atmospheric pressure Answer: a) The changes in density and temperature The “Mach number” can be determined from: a) The ratio of the local speed of sound to the flow velocity b) The ratio of the static pressure to the total pressure c) The ratio of the dynamic pressure to the static pressure d) The ratio of the total temperature to the static temperature Answer: a) The ratio of the local speed of sound to the flow velocity The “non-dimensional” number used to characterize compressibility effects is the: a) Mach number b) Reynolds number c) Prandtl number d) Nusselt number Answer: a) Mach number The “Rankine-Hugoniot” relations describe: a) The conservation laws across a shock wave b) The flow characteristics in an isentropic expansion c) The temperature distribution in a nozzle d) The pressure drop in a turbulent boundary layer Answer: a) The conservation laws across a shock wave In the “oblique shock wave,” the flow deflection angle depends on: a) The Mach number and the shock angle b) The temperature and pressure of the flow c) The density and viscosity of the fluid d) The boundary layer thickness and the Reynolds number Answer: a) The Mach number and the shock angle The “total temperature” in compressible flow is: a) The temperature measured when the flow is brought to rest b) The static temperature plus the dynamic temperature c) The temperature at the nozzle exit d) The temperature adjusted for frictional effects Answer: a) The temperature measured when the flow is brought to rest The “isentropic” flow relations assume: a) Adiabatic and reversible processes b) Isothermal and irreversible processes c) Constant pressure and constant temperature conditions d) Steady and incompressible flow Answer: a) Adiabatic and reversible processes The “Mach wave” is generated by: a) A disturbance traveling at the speed of sound b) A flow deflected by an obstacle c) A pressure change across a shock wave d) A sudden change in temperature Answer: a) A disturbance traveling at the speed of sound In “supersonic” flow, the “conservation of mass” leads to: a) A decrease in density with an increase in flow area b) An increase in pressure with a decrease in flow velocity c) A constant flow velocity with a variable density d) A constant temperature with a variable pressure Answer: a) A decrease in density with an increase in flow area The “nozzle efficiency” in gas dynamics is defined as: a) The ratio of the actual thrust to the theoretical thrust b) The ratio of the actual pressure to the ideal pressure c) The ratio of the exit velocity to the throat velocity d) The ratio of the total temperature to the static temperature Answer: a) The ratio of the actual thrust to the theoretical thrust The “Mach number” at the throat of a converging-diverging nozzle is: a) 1 b) 0.5 c) 2 d) 0.8 Answer: a) 1 In “high-speed aerodynamics,” the “compressibility effect” becomes significant when: a) The Mach number exceeds 0.3 b) The flow is subsonic c) The Mach number is close to 1 d) The velocity is below the speed of sound Answer: c) The Mach number is close to 1 The “entropy” in gas dynamics represents: a) A measure of disorder or randomness in the system b) The heat added to the system at constant pressure c) The work done by the system in an adiabatic process d) The temperature change in a reversible process Answer: a) A measure of disorder or randomness in the system The “Bernoulli equation” for compressible flow is modified by including: a) The term for the change in density b) The term for the heat added or removed c) The term for frictional losses d) The term for the change in velocity Answer: a) The term for the change in density The “isentropic flow” assumptions are applied to: a) Ideal gases undergoing adiabatic and reversible processes b) Real gases undergoing heat transfer and friction c) Steady flow with constant pressure and temperature d) Turbulent flow with significant heat exchange Answer: a) Ideal gases undergoing adiabatic and reversible processes The “sensible heat” in gas dynamics refers to: a) The heat added to the gas that changes its temperature b) The heat absorbed by the gas without changing its temperature c) The heat lost to the surroundings in a constant-pressure process d) The heat transferred during a phase change Answer: a) The heat added to the gas that changes its temperature The “Mach cone” is a result of: a) The interaction of pressure waves emitted by a moving object b) The change in velocity across a shock wave c) The expansion of gases in a high-speed nozzle d) The curvature of the airfoil in subsonic flight Answer: a) The interaction of pressure waves emitted by a moving object The “total pressure” in compressible flow is: a) The pressure measured when the flow is brought to rest b) The pressure at the nozzle exit c) The pressure drop across a shock wave d) The pressure at the throat of a nozzle Answer: a) The pressure measured when the flow is brought to rest In “compressible flow,” the “isentropic efficiency” is used to: a) Evaluate the performance of compressible flow devices b) Measure the impact of turbulence on the flow c) Determine the boundary layer thickness d) Assess the effects of heat transfer on the flow Answer: a) Evaluate the performance of compressible flow devices The “Mach number” at the exit of a converging-diverging nozzle can be: a) Supersonic b) Subsonic c) Sonic d) Zero Answer: a) Supersonic The “entropy” change in an adiabatic process is: a) Zero b) Positive c) Negative d) Depends on the type of gas Answer: a) Zero The “choking” condition in a nozzle occurs when: a) The flow reaches the speed of sound at the nozzle throat b) The pressure at the nozzle exit is zero c) The flow velocity is maximum at the nozzle exit d) The temperature in the nozzle is constant Answer: a) The flow reaches the speed of sound at the nozzle throat The “total energy” in a gas flow is the sum of: a) Kinetic energy and potential energy b) Internal energy and flow work c) Static energy and dynamic pressure d) Internal energy and kinetic energy Answer: d) Internal energy and kinetic energy The “Rayleigh line” in gas dynamics represents: a) The relationship between velocity and temperature for a given pressure b) The pressure drop across a shock wave c) The expansion of gases in a converging-diverging nozzle d) The flow characteristics in a nozzle with heat addition or removal Answer: d) The flow characteristics in a nozzle with heat addition or removal The “conservation of energy” in compressible flow is described by: a) The energy equation b) The continuity equation c) The momentum equation d) The Bernoulli equation Answer: a) The energy equation The “Mach number” at the nozzle throat of a converging-diverging nozzle is always: a) 1 b) Less than 1 c) Greater than 1 d) Zero Answer: a) 1 The “speed of sound” in a gas is affected by: a) Temperature and pressure b) The gas composition and velocity c) The density and viscosity of the gas d) The altitude and humidity Answer: a) Temperature and pressure The “total enthalpy” in gas dynamics is given by: a) The sum of the static enthalpy and the dynamic pressure b) The sum of the internal energy and the flow work c) The static enthalpy plus the kinetic energy per unit mass d) The temperature plus the pressure term Answer: c) The static enthalpy plus the kinetic energy per unit mass

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