ame: 1. (S points each) Imagine a flat plate with length L is placed in a viscou

Question

ame: 1. (S points each) Imagine a flat plate with length L is placed in a viscous, parallel flow what happens to each of the following parameters when this occurs, assuming the flow is laminar both before and after the change. with a given velocity and temperature. Suddenly, the velocity is doubled. Identify What happens? Parameter Reynolds number Prandtl number Nusselt number Stays the same Stays the same Stays the same Stays the same Stays the same es Increases Increases Average shear stress Increases Boundary layer thickness at Increases plate midpoint 2 (5 points each) Imagine two flat plates of identical size, material, and temperature are placed in a viscous, parallel flow for which Re = 2 x 10s. The first flat plate is completely smooth, while the second has a trip wire at the leading edge to induce turbulence. Identify which plate has a greater value of each parameter. Parameter Where is it larger? First plateSecond plate Same for each Reynolds number Prandtl number Nusselt number First plateSecond plate First plate Second plate Second plate Same for each Same for each Same for each Second plate Same for each Average shear stress coefficient First plate Rate of heat transfer First plate

Explanation / Answer

1. reynolds number increases as it is given by Re = pvl/u

where u = viscosity,p= density ,l=length of plate,v= velocity

prandtl number remain the same as it the ratio of viscus diffusion rate to thermal diffusion rate .

nusselt number also be the same as it is given by Nu = hl/k

where Nu= nusselt number ,h=convective heat transfer coeffient,l=characteristic length,k=thermal conductivity

aveage shear stress coefficient will also be the same

boundary layer thickness at mid of plate will decrease as it sepends on reynolds number as reynolds number increases boundary layer decreases.

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