How to save planarAvg results as 2D data?

[foreverkon]

Hello,

I’ve been using the planarAvg function and noticed that the output is always given as a 3D field, even though the averaged result is essentially 1D or 2D depending on the averaging direction.

For post-processing purposes, it would be very helpful if we could save only a 2D slice (or a 1D profile) instead of the full 3D array.

Is there currently a built-in way to output the planar-averaged result in a lower-dimensional form?

[yslan]

See the ktauChannel example to extract values on desired points.

nekRS/examples/ktauChannel/channel.udf

Lines 29 to 83 in 96b3cf9

	void extractLine(nrs_t *nrs, double time)
	{
	const auto np = (platform->comm.mpiRank() == 0) ? 200 : 0;
	const auto offset = np;
	static pointInterpolation_t *interpolator = nullptr;
	static std::vector<dfloat> xp, yp, zp;
	static deviceMemory<dfloat> o_Up;
	if (!interpolator) {
	auto mesh = nrs->meshV;
	const auto yMin = platform->linAlg->min(mesh->Nlocal, mesh->o_y, platform->comm.mpiComm());
	const auto yMax = platform->linAlg->max(mesh->Nlocal, mesh->o_y, platform->comm.mpiComm());
	if (np) {
	const auto x0 = 7.0;
	const auto z0 = 0.5;
	xp.push_back(x0);
	yp.push_back(yMin);
	zp.push_back(z0);
	const auto betaY = 2.2;
	const auto dy = (yMax - yMin) / (np - 1);
	for (int i = 1; i < np - 1; i++) {
	xp.push_back(x0);
	yp.push_back(tanh(betaY * (i * dy - 1)) / tanh(betaY));
	zp.push_back(z0);
	}
	xp.push_back(x0);
	yp.push_back(yMax);
	zp.push_back(z0);
	o_Up.resize(mesh->dim * offset);
	}
	interpolator = new pointInterpolation_t(mesh, platform->comm.mpiComm());
	interpolator->setPoints(xp, yp, zp);
	interpolator->find();
	}
	interpolator->eval(nrs->meshV->dim, nrs->fluid->fieldOffset, nrs->fluid->o_U, offset, o_Up);
	if (platform->comm.mpiRank() == 0) {
	std::vector<dfloat> Up(nrs->meshV->dim * np);
	o_Up.copyTo(Up);
	std::ofstream f("profile.dat", std::ios::app);
	for (int i = 0; i < np; i++) {
	f << std::scientific << time << " " << xp[i] << " " << yp[i] << " " << zp[i] << " "
	<< Up[i + 0 * offset] << " " << Up[i + 1 * offset] << " " << Up[i + 2 * offset] << std::endl;
	}
	f.close();
	}
	}

[foreverkon]

Thanks! It's helpful.