Turbulence Modelling MCQ

Test your knowledge with important Turbulence Modelling MCQ and their applications. These MCQs are beneficial for competitive exams too. Explore 30 + more Turbulence Modelling MCQs at Bissoy

• Which of these models is a hybrid of LES and RANS?
  ক

  DNS model

  খ

  DES model

  গ

  WALE model

  ঘ

  RNG – LES model
• Which of these models solves turbulent kinetic energy and specific dissipation?
  ক

  K – omega model

  খ

  K – epsilon model

  গ

  RANS model

  ঘ

  RNG – LES model
• Which of these is a two – equation model?
  ক

  Baldwin – Lomax model

  খ

  Prandtl’s equation model

  গ

  Spalart – Allmaras model

  ঘ

  K – Epsilon model
• One equation turbulence model account for the history effects such as turbulent energy, diffusion and convection.
  ক

  True

  খ

  False
• Which of these models compute large vortexes directly while neglecting small scale eddies?
  ক

  DNS

  খ

  LES

  গ

  RANS

  ঘ

  FANS
• What are the shortcomings of DNS?
  ক

  Possible for low Reynolds number

  খ

  Low scale resolution

  গ

  Time consuming

  ঘ

  Possible for high Reynolds number
• Why are turbulence models used?
  ক

  Define reynolds stress for closure problems

  খ

  Model hypersonic flows

  গ

  Lack of system to accurately find turbulent flow characteristic

  ঘ

  Closure of continuity equation
• Turbulent boundary layer is considered to be a combination of inner and outer layer.
  ক

  True

  খ

  False
• ___________ creates a problem in the SGS models.
  ক

  Low Reynolds number flows

  খ

  High Reynolds number flows

  গ

  Anisotropic flow near the wall

  ঘ

  Viscous flow near the wall
• The SGS model uses _________ to reduce the sub-grid-scale eddy viscosity near the wall.
  ক

  van Karman’s constant

  খ

  van Driest damping

  গ

  wall function

  ঘ

  Leonard stresses
• The Smagorinsky-Lilly SGS model is ___________
  ক

  Dissipative

  খ

  Convective

  গ

  Diffusive

  ঘ

  Convective and diffusive
• In the higher-order SGS model, what is the velocity scale used?
  ক

  The ratio of the SGS turbulent kinetic energy to the SGS eddy viscosity

  খ

  The product of the SGS turbulent kinetic energy and the SGS eddy viscosity

  গ

  The square root of the SGS eddy viscosity

  ঘ

  The square root of the SGS turbulent kinetic energy
• Which of these assumptions is made in the Smagorinsky-Lilly SGS model?
  ক

  The changes in the flow direction are slow in the resolved flow

  খ

  The changes in the cross-stream direction are slow in the resolved flow

  গ

  The changes in the flow direction are slow in the SGS eddies

  ঘ

  The changes in the cross-stream direction are slow in the SGS eddies
• The characteristic length of the SGS eddies is __________
  ক

  half of the filter cut-off width

  খ

  the filter cut-off width

  গ

  twice the filter cut-off width

  ঘ

  thrice the filter cut-off width
• According to the Smagorinsky-Lilly SGS model, the SGS stresses depend on the ___________
  ক

  Rate of strain of the SGS eddies

  খ

  Rate of strain of the resolved flow

  গ

  Strain of the resolved flow

  ঘ

  Strain of the SGS eddies
• The Smagorinsky-Lilly (Sub-Grid-Scale) SGS model uses ___________
  ক

  Boussinesq hypothesis and Prandtl mixing length model

  খ

  Prandtl mixing length model and k-ε model

  গ

  k-ε model and k-ω model

  ঘ

  k-ω model and Boussinesq hypothesis
• LES Reynolds stresses are caused by ____________
  ক

  Source term

  খ

  Resolved flow

  গ

  SGS eddies

  ঘ

  Diffusion term
• The SGS stresses are obtained from ___________
  ক

  Reynolds stress term

  খ

  Convection term

  গ

  Source term

  ঘ

  Diffusion term
• How many extra stress terms occur due to the LES filtering operation?
  ক

  No extra terms

  খ

  Four terms

  গ

  Three terms

  ঘ

  Two terms
• When is the LES filter commutative?
  ক

  When the filter function is unity

  খ

  When the filter function is quadratic

  গ

  When the filter function is isotropic

  ঘ

  When the filter function is uniform
• The range of values of the turbulent kinetic energy is ___________
  ক

  50 to 75%

  খ

  11 to 20%

  গ

  1 to 10%

  ঘ

  0 to 1%
• Which of these is correct about the first internal node of a k-ε model?
  ক

  k-equation is not solved

  খ

  ε-equation is not solved

  গ

  Both k and ε-equations are not solved

  ঘ

  Both k and ε-equations are solved simultaneously
• When k and ε values are not available, for inlet boundary conditions, they are ____________
  ক

  obtained from turbulence intensity

  খ

  assumed to be zero

  গ

  assumed to be unity

  ঘ

  obtained from Reynolds number
• In the low Reynolds number turbulence models, the first internal grid point is placed in the ___________
  ক

  log-law layer

  খ

  buffer layer

  গ

  inertial sub-layer

  ঘ

  viscous sub-layer
• Which of these values vanish near the wall boundary?
  ক

  Velocity and turbulent viscosity

  খ

  Velocity and Reynolds number

  গ

  Velocity and k-value

  ঘ

  k-value and Reynolds number
• Boundary conditions near the solid-walls for a k-ε model depends on ___________
  ক

  Eddy viscosity

  খ

  Reynolds number

  গ

  ε-value

  ঘ

  k-value
• The value of y+ at the intersection between the linear profile and log-law is ___________
  ক

  20

  খ

  5

  গ

  30

  ঘ

  11.63
• The value of y+ is 50. Which layer does it belong to?
  ক

  Inertia dominated layer

  খ

  Velocity defect layer

  গ

  Log-law layer

  ঘ

  Law of the wake layer
• What is the range of y+ in the buffer layer?
  ক

  0 < y+ < 5

  খ

  5 < y+ < 30

  গ

  30 < y+ < 500

  ঘ

  10 < y+ < 20
• Wall function cannot be used when ___________
  ক

  y+<30

  খ

  y+>30

  গ

  y+<20

  ঘ

  y+>20