Adding test cases for reading of fourier coefficient file (#427)

* fix read io bug and add test for fft

* add python script for fft compute

* updated .vtu file for test

* minor comments

* added header file for test_ftt unit test

* added copyright

* addresses minor comments and changes description

* improved .fcs precision and removed files where not needed

* updated README for fcs

* added utilities directory that contains python script for fcs generation

* minor edit to README

---------

Co-authored-by: Aaron Brown <[email protected]>

Author: kko27

Code/Source/solver/read_files.cpp

@@ -1935,10 +1935,9 @@ void read_fourier_coeff_values_file(const std::string& file_name, bcType& lBc)
       values.push_back(value);
     }
 
-    int num_vals = values.size();
-    for (int i = 0; i < values.size(); i++) {
-      lBc.gt.r(i,j) = values[i]; 
-      lBc.gt.i(i,j) = values[i+num_vals];
+    for (int i = 0; i < lBc.gt.d; i++) { 
+      lBc.gt.r(i,j) = values[i];
+      lBc.gt.i(i,j) = values[i + lBc.gt.d];
     }
 
     j += 1;
@@ -2004,10 +2003,9 @@ void read_fourier_coeff_values_file(const std::string& file_name, bfType& lBf)
       values.push_back(value);
     }
 
-    int num_vals = values.size();
-    for (int i = 0; i < values.size(); i++) {
-      lBf.bt.r(i,j) = values[i]; 
-      lBf.bt.i(i,j) = values[i+num_vals];
+    for (int i = 0; i < lBf.bt.d; i++) { 
+      lBf.bt.r(i,j) = values[i];
+      lBf.bt.i(i,j) = values[i + lBf.bt.d];
     }
 
     j += 1;

tests/cases/fluid/pipe_RCR_3d/lumen_inlet.fcs

@@ -0,0 +1,19 @@
+
+# **Problem Description**
+
+Simulate unsteady fluid flow in a pipe. This case is identical to <a href="https://github.com/SimVascular/svFSIplus/tree/main/tests/cases/fluid/pipe_RCR_3d"> Fluid RCR 3D Pipe </a>, except that fourier coefficients are read by the solver (instead of the usual temporal values file). For additional validation, the **results_002.vtu** output file used in this case is the same as the `pipe_RCR_3d` case. 
+
+# Inlet flow boundary condition
+
+Interpolated Fourier coefficients are provided for the **lumen_inlet** boundary condition. These coefficients are specified in the **lumen_inlet.fcs** file, which is an alternative to the flow data that is provided in the **lumen_inlet.flow**. Providing the fourier coefficient file skips the fourier interpolation function (**fft.cpp**) in svMultiphysics. Documentation on the file format can be accessed [here](https://simvascular.github.io/documentation/multi_physics.html#data_file_formats_boundary_condition_fourier) and the `lumen_inlet` boundary condition block is provided in the [solver.xml](./solver.xml). 
+
+The **lumen_inlet.fcs** file can be generated using the **fft_temporal_values.py** which is available in the `utilities` directory ([here](../../../../utilities/fourier_coefficients/)). This script takes the lumen_inlet.flow file, computes the Fourier coefficients using an identical fft python function, and returns the **.fcs** file ready for simulation. It also provides a visualization of the fourier interpolation, which is shown below:
+
+<p align="center">
+   <img src="./fft_reconstruction.png" width="600">
+</p>
+
+
+# Outlet RCR boundary condition
+
+An RCR boundary condition is defined for the **lumen_outlet** outlet face.

tests/cases/fluid/pipe_RCR_3d_fourier_coeff/README.md

@@ -0,0 +1,19 @@
+0.0 1.0
+0.0 0.0
+16
+-6.2831852968750006e+01    0.0000000000000000e+00
+6.2630248089319764e+01    -1.8689837176965406e-07
+-1.8510278462895881e-07    1.2598780427743684e-15
+-3.2931465665672273e-07    1.8214078224321383e-07
+2.9676287399904954e-07    -2.2497822192399436e-16
+-7.1346109986563247e-07    -1.7291577648812070e-07
+-1.6679265373961399e-07    4.9995160427554296e-16
+-1.9207332282283037e-06    1.5978005149412804e-07
+5.0660591524529525e-08    -2.5872495521259351e-16
+9.3646292551129305e-07    -1.4351166349130110e-07
+-1.3449131704204189e-07    3.5996515507839091e-18
+-9.4105400926950758e-07    1.2504770956829968e-07
+1.9218453262995655e-07    8.7491530748220019e-18
+9.5400603135350799e-07    -1.0541065198628774e-07
+-9.5475796377833937e-08    -1.1065255404833191e-16
+1.0167834071836435e-06    8.5630083711416610e-08

tests/cases/fluid/pipe_RCR_3d_fourier_coeff/fft_reconstruction.png

@@ -0,0 +1,34 @@
+33    16
+0.000000    0.000000
+0.031250    -1.207301
+0.062500    -4.782786
+0.093750    -10.589077
+0.125000    -18.403023
+0.156250    -27.924348
+0.187500    -38.787146
+0.218750    -50.573962
+0.250000    -62.83185
+0.281250    -75.089744
+0.312500    -86.876560
+0.343750    -97.739358
+0.375000    -107.260684
+0.406250    -115.074629
+0.437500    -120.880920
+0.468750    -124.456405
+0.500000    -125.663706
+0.531250    -124.456405
+0.562500    -120.880920
+0.593750    -115.074629
+0.625000    -107.260684
+0.656250    -97.739358
+0.687500    -86.876560
+0.718750    -75.089744
+0.750000    -62.831853
+0.781250    -50.573962
+0.812500    -38.787146
+0.843750    -27.924348
+0.875000    -18.403023
+0.906250    -10.589077
+0.937500    -4.782786
+0.968750    -1.207301
+1.000000    0.000000

tests/cases/fluid/pipe_RCR_3d_fourier_coeff/lumen_inlet.fcs

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:75e318c829105bb00e353522f1697361444d6199f92da1dc374927f243ea7632
+size 176990

tests/cases/fluid/pipe_RCR_3d_fourier_coeff/lumen_inlet.flow

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b77b872930b3ff01f8bc6e3ea6e061a4df800ba3bc1f4d4bf3a275f863022cea
+size 6972

tests/cases/fluid/pipe_RCR_3d_fourier_coeff/mesh/mesh-complete.mesh.vtu

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:c5c16563fee4011b1e89bd3492dd2798de2185dfcfb9b60944a3155a50f13187
+size 7070

tests/cases/fluid/pipe_RCR_3d_fourier_coeff/mesh/mesh-surfaces/lumen_inlet.vtp

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:3e3dfb1b920d6ddb3066c84a3564069541a3c8b0c2ebedad2a58625d5369de1b
+size 66024