A simple tool taking a .vdb in input and write a kind of raw file in output.
If you don't want to compile the tool by yourself, you can find a precompiled win64 executable in the /release directory.

You need to install openvdb first.
The easiest way is to use vcpkg via :
vcpkg install openvdb:x64-windows
Make sure you have already launched vcpkg Integrate install once, to integrate vcpkg with Visual Studio.

vdb2raw smoke.vdb
-> density_191x610x178.raw : 100 %
value min/max : 0 / 0.4854

The output file contains :
width, height, depth in int
data[] in float

#include <fstream>

std::ifstream file("density_191x610x178.raw", std::ifstream::binary);
int dim[3];
file.read((char*)dim, sizeof(int) * 3);
int nbVoxels = dim[0] * dim[1] * dim[2];
float* data = new float[nbVoxels];
file.read((char*)data, sizeof(float) * nbVoxels);