ENH: FFT - removed power-of-2 constraint on number of samples

applications/utilities/postProcessing/noise/noise.C

@@ -74,8 +74,7 @@ Usage
             }
         }
 
-        // Number of samples in sampling window
+        // Number of samples in sampling window, default = 2^16 (=65536)
-        // Must be a power of 2, default = 2^16 (=65536)
         N               4096;
 
         // Write interval for FFT data, default = 1

applications/utilities/postProcessing/noise/noiseDict

@@ -72,8 +72,7 @@ surfaceNoiseCoeffs
     // Reference density (to convert from kinematic to static pressure)
     rhoRef          1.205;
 
-    // Number of samples in sampling window
+    // Number of samples in sampling window, default = 2^16 (=65536)
-    // Must be a power of 2, default = 2^16 (=65536)
     N               4096; // 8192; // 4096;
 
     // Lower frequency limit, default = 25Hz
@@ -123,8 +122,7 @@ pointNoiseCoeffs
     // Reference density (to convert from kinematic to static pressure)
     rhoRef          1.2;
 
-    // Number of samples in sampling window
+    // Number of samples in sampling window, default = 2^16 (=65536)
-    // Must be a power of 2, default = 2^16 (=65536)
     N               4096;
 
     // Lower frequency limit, default = 25Hz

src/randomProcesses/fft/fft.C

@@ -95,20 +95,6 @@ void Foam::fft::transform
     transformDirection dir
 )
 {
-    forAll(nn, idim)
-    {
-        // Check for power of two
-        unsigned int dimCount = nn[idim];
-        if (!dimCount || (dimCount & (dimCount - 1)))
-        {
-            FatalErrorInFunction
-                << "number of elements in direction " << idim
-                << " is not a power of 2" << endl
-                << "    Number of elements in each direction = " << nn
-                << abort(FatalError);
-        }
-    }
-
     // Copy field into fftw containers
     const label N = field.size();
     fftw_complex in[N], out[N];

src/randomProcesses/noise/noiseModels/noiseModel/noiseModel.C

@@ -206,16 +206,6 @@ bool Foam::noiseModel::read(const dictionary& dict)
     dict.readIfPresent("maxPressure", maxPressure_);
     dict.readIfPresent("outputPrefix", outputPrefix_);
 
-    // Check number of samples  - must be a power of 2 for our FFT
-    bool powerOf2 = ((nSamples_ != 0) && !(nSamples_ & (nSamples_ - 1)));
-    if (!powerOf2)
-    {
-        FatalIOErrorInFunction(dict)
-            << "N: Number of samples in sampling windows must be a "
-            << "power of 2"
-            << exit(FatalIOError);
-    }
-
     if (fLower_ < 0)
     {
         FatalIOErrorInFunction(dict)

src/randomProcesses/noise/noiseModels/noiseModel/noiseModel.H

@@ -66,9 +66,6 @@ Description
         writeOctaves | Write octaves data            | no        | yes
     \endtable
 
-Note
-    The number of samples in the sampling window must be a power of 2
-
 
 SourceFiles
     noiseModel.C

src/randomProcesses/noise/noiseModels/pointNoise/pointNoise.H

@@ -33,8 +33,7 @@ Description
     // Pressure reference
     pRef            0;
 
-    // Number of samples in sampling window
+    // Number of samples in sampling window, default = 2^16 (=65536)
-    // Must be a power of 2, default = 2^16 (=65536)
     N               4096;
 
     // Lower frequency bounds

src/randomProcesses/noise/noiseModels/surfaceNoise/surfaceNoise.H

@@ -33,8 +33,7 @@ Description
     // Pressure reference
     pRef            0;
 
-    // Number of samples in sampling window
+    // Number of samples in sampling window, default = 2^16 (=65536)
-    // Must be a power of 2, default = 2^16 (=65536)
     N               4096;
 
     // Lower frequency bounds

tutorials/incompressible/pimpleFoam/LES/vortexShed/system/noiseDict-point

@@ -45,7 +45,7 @@ pointNoiseCoeffs
     separator       " ";
 
     // Number of samples in sampling window
-    // Must be a power of 2, default = 2^16 (=65536)
+    // default = 2^16 (=65536)
     N               4096;
 
     rhoRef          1.205;

tutorials/incompressible/pimpleFoam/LES/vortexShed/system/noiseDict-surface

@@ -56,7 +56,7 @@ surfaceNoiseCoeffs
     p               Curle;
 
     // Number of samples in sampling window
-    // Must be a power of 2, default = 2^16 (=65536)
+    // default = 2^16 (=65536)
     N               1024;
 
     rhoRef          1.205;