# The BC is not exterior surface Answered

Hi，

The picture is my BC . The print file says boundary is not exterior surface and k =2.But my model is 2D.The k should be equal to 0.Why does it say k=2 when the BC is set like this?

If I set the BC to following,the absorbing boundary doesn't absorb ultrasonic and will report 'bad value' error.

boun

side xmin free

side xmax absr

side ymin free

side ymax absr

end

How should I set the BC?

Best regards，

Enclosed here is the node list.

x1 ( real ) = 0.000000

x2 ( real ) = 0.8000000E-03

x3 ( real ) = 0.8608000

x4 ( real ) = 0.8618000

idx ( integer ) = 4

xmax ( real ) = 0.8618000

y1 ( real ) = 0.000000

y2 ( real ) = 0.1625000E-01

y3 ( real ) = 0.3625000E-01

y4 ( real ) = 0.4625000E-01

y5 ( real ) = 0.6625000E-01

y6 ( real ) = 0.7625000E-01

y7 ( real ) = 0.9625000E-01

y8 ( real ) = 0.1062500

y9 ( real ) = 0.1262500

y10 ( real ) = 0.1362500

y11 ( real ) = 0.1562500

y12 ( real ) = 0.1662500

y13 ( real ) = 0.1862500

y14 ( real ) = 0.1962500

y15 ( real ) = 0.2162500

y16 ( real ) = 0.2262500

y17 ( real ) = 0.2462500

jaend ( integer ) = 17

y18 ( real ) = 0.3300000

jdx ( integer ) = 18

ymax ( real ) = 0.3300000

i1 ( integer ) = 1

i2 ( integer ) = 9

i3 ( integer ) = 8072

i4 ( integer ) = 8081

indgrd ( integer ) = 8081

j1 ( integer ) = 1

j2 ( integer ) = 153

j3 ( integer ) = 341

j4 ( integer ) = 435

j5 ( integer ) = 622

j6 ( integer ) = 716

j7 ( integer ) = 903

j8 ( integer ) = 997

j9 ( integer ) = 1184

j10 ( integer ) = 1278

j11 ( integer ) = 1465

j12 ( integer ) = 1559

j13 ( integer ) = 1746

j14 ( integer ) = 1840

j15 ( integer ) = 2027

j16 ( integer ) = 2121

j17 ( integer ) = 2308

j18 ( integer ) = 3093

jndgrd ( integer ) = 3093

## 3 comments

Oliver MashariAbsorbin boundary conditions need to be placed on the extents/exterior/limits of the model you have specified the nodal location i3-1 looking at your node map i4 lies on the exterior of the model.

Hxd-ndtI understand.But the node i3 is the boudary of the geometry and the i4 is the boundary of the model.If I set both of them absr, it the i3 absorbing boundary doesn't absorb ultrasonic and will report 'bad value' error.

Oliver MashariWhat model is this for we are currently looking at or plan to look at other models you have shared, just to gie me a better understanding of the variables you posted above

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