Fluid dynamicist here. The $\beta$ notation appears to be a convenient way to write the Laplacian assuming that the temperature is homogeneous in the angular di

Fluid dynamicist here. The $\beta$ notation appears to be a convenient way to write the Laplacian assuming that the temperature is homogeneous in the angular direction. The values are exact for certain coordinate systems. https://en.wikipedia.org/wiki/Laplace_operator#Three_dimensions https://en.wikipedia.org/wiki/Laplace_operator#Three_dimensi...