Computational Fluid Dynamics Questions With Complete Solutions

Typical shapes of unstructured grid cells used in 2D grids are quadrilateral and ______________________ correct answer: triangular a grid is ___________ if any line connecting centers of neighboring cells face between the cells correct answer: orthogonal one disadvantage of using unstructured grids is slower _____________ correct answer: convergence it is recommended for flows with attached boundary layers that the grid includes a layer of thin quadrilateral or hexahedral cells adjacent to the _______________ correct answer: wall hexahedra, __________________, prisms, and pyramids are typical shapes of unstructured grid cells used in 3D grids correct answer: tetrahedra triangular or tetrahedral cells have geometric advantages of easily fitting in arbitrary geometry and generating nearly _____________ grids correct answer: orthogonal central difference approximation of derivatives and linear interpolation are more accurate on rectangular or ____________ cells correct answer: hexahedral complex _____________ is one of the reasons we need irregular grid correct answer: geometry _______________ grid is a grid which is not structured, rectangular, or uniform correct answer: irregular Smagorinsky constant varies from .1 in flows with _______________ shear to .17 in flows without shear correct answer: strong LES is more accurate than ____________________ especially in reproducing flows with large scale unsteady features correct answer: RANS for turbulent simulations LES stands for ____________________ eddy simulations correct answer: large K is turbulent kinetic energy and E (lower case epsilon) is rate of viscous ________________ in the K-E (epsilon) model correct answer: dissipation in the _______________ models the velocity Q(x,t) and length l(x,t) scales are determined as solutions of two additional PDE's correct answer: 2-Equation RANS stands for reynolds _______________