Mechanical APDL Basic Analysis Guide

Y

X = 1 Regime 1 X = 5 Regime 2 X = 10

Convection Boundary

Condition

Constant temperature

The bottom of the plate is fixed at a constant temperature. The top of the plate, where the convection
boundary condition is being applied, is split into two regimes:

Regime 1 is defined for X between 1 ≤ X<5, and the convection heat transfer coefficient is given by:

h(x) = 0.332 (kxx/x) Re*(1/2) Pr**(1/3)

Regime 2 is defined for X between 5 < X ≤ 10, and the convection heat transfer coefficient is given
by:

h(x) = 0.566 (kxx/x) Re*(1/2) Pr**(1/3)

In the above equations, the Reynolds number Re is given by:

Re = (densvelx)/visc

and the Prandtl number PR is given by:

Pr = (visc*c)/kxx

The properties of the fluid over the flat plate are:

Density (dens) = 1, thermal conductivity (kxx) = 10, specific heat (c) = 10, and viscosity (visc) = 0.01

The velocity of the fluid (vel) over the flat plate is equal to 100 for Regime 1 and 50 for Regime 2. Bulk
temperature for the fluid for both regimes is 100 degrees.

1. Create a rectangle and assign element type PLANE55, define your material properties, and mesh:

/prep7

rect,1,10,,.5

et,1,55

!Define Fluid Properties

mp,KXX,1,10 !Thermal conductivity

mp,DENS,1,1 !Density

mp,C,1,10 !Specific heat

mp,VISC,1,0.01 !Viscosity

!Define Plate Properties

mp,kxx,2,10

mp,dens,2,10

mp,c,2,5

mat,2

esize,,25

amesh,all

2. Define the convection boundary condition as a function.

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Function Tool Example