# why pressure increases a lot at wall corner?

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February 5, 2013, 14:38
why pressure increases a lot at wall corner?
#1
Senior Member

Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,210
Rep Power: 19
I use this condition for p at outlet:
Code:
`p0_2/pow(part1,3.5)`
when :
Code:
`"part1=1+(gamma-1)/2*sqr(internalField(U.x))/(gamma*R*internalField(T));"`
these all make the well-known isentropic relation.
but at the corner where there is a wall a cell makes troubles for all the solution.why this behaves so at corner of outlet?
my whole BC for p is like below that I extrude above relations from that:
Code:
```right
{
type groovyBC;

variables (

"r=0.02325;"
"rpm=25899.28055;"
"omega=rpm*pi/30;"
"v_r=r*omega;"
"w_cell=.004;"
"n=1;"

"w_w0=n*w_cell;"
"w_w3=(21.6-0)*r*pi/180;"
"w_w4=(83-61.6)*r*pi/180;"
"w_w5=(180-128)*r*pi/180;"
"w_p2=(71.1-21.6)*r*pi/180;"
"w_p4=(129-84)*r*pi/180;"

"c1=w_p2/v_r;"
"c2=(w_p2+w_w4)/v_r;"
"c3=(w_p2+w_w4+w_p4)/v_r;"
"c4=(w_p2+w_w4+w_p4+w_w5+w_w3)/v_r;"
"t1=(w_w0+w_w3-pos().y)/v_r;"
"t2=t1+c4;"
"t3=t1+2*c4;"
"t4=t1+3*c4;"
"t5=t1+4*c4;"
"t6=t1+5*c4;"
"t7=t1+6*c4;"
"t8=t1+7*c4;"
"t9=t1+8*c4;"
"t10=t1+9*c4;"
"t11=t1+10*c4;"

"p0_2=1023382.5;"
"T0_2=907;"
"p0_4=374902.5;"
"T0_4=973;"
"gamma=1.4;"
"R=287.14;"
"part1=1+(gamma-1)/2*sqr(internalField(U.x))/(gamma*R*internalField(T));"
"part2_inflow=1-(gamma-1)*magSqr(internalField(U))/(2*gamma*R*T0_2);"
"part4_inflow=1-(gamma-1)*magSqr(internalField(U))/(2*gamma*R*T0_4);"

);

fractionExpression "(t1<time()&&time()<t1+c1)||(t2<time()&&time()<t2+c1)||(t3<time()&&time()<t3+c1)||(t4<time()&&time()<t4+c1)||(t5<time()&&time()<t5+c1)||(t6<time()&&time()<t6+c1)||(t7<time()&&time()<t7+c1)||(t8<time()&&time()<t8+c1)||(t9<time()&&time()<t9+c1)||(t10<time()&&time()<t10+c1)||(t11<time()&&time()<t11+c1)||((t1+c2<time()&&time()<t1+c3)||(t2+c2<time()&&time()<t2+c3)||(t3+c2<time()&&time()<t3+c3)||(t4+c2<time()&&time()<t4+c3)||(t5+c2<time()&&time()<t5+c3)||(t6+c2<time()&&time()<t6+c3)||(t7+c2<time()&&time()<t7+c3)||(t8+c2<time()&&time()<t8+c3)||(t9+c2<time()&&time()<t9+c3)||(t10+c2<time()&&time()<t10+c3)||(t11+c2<time()&&time()<t11+c3))&&(mag(internalField(U))/sqrt(gamma*R*internalField(T))<1)?1:0";
valueExpression "(t1<time()&&time()<t1+c1)||(t2<time()&&time()<t2+c1)||(t3<time()&&time()<t3+c1)||(t4<time()&&time()<t4+c1)||(t5<time()&&time()<t5+c1)||(t6<time()&&time()<t6+c1)||(t7<time()&&time()<t7+c1)||(t8<time()&&time()<t8+c1)||(t9<time()&&time()<t9+c1)||(t10<time()&&time()<t10+c1)||(t11<time()&&time()<t11+c1)?((phi>=0)?p0_2/pow(part1,3.5):p0_2*pow(part2_inflow,3.5)):((phi>0)?p0_4/pow(part1,3.5):p0_4*pow(part4_inflow,3.5))";
value uniform 1023382.5;
}```
Attached Images
 corner.jpg (11.9 KB, 13 views)

February 5, 2013, 14:43
#2
Senior Member

Ehsan
Join Date: Oct 2012
Location: Iran
Posts: 2,210
Rep Power: 19
also U becomes very much around the outlet corner.
Attached Images
 corner_velocity.jpg (11.1 KB, 7 views)

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