Thank you as always
I want to calculate the particle velocity by analysis using kspace_FirstOrder3d.m.
I think there are two ways to do this.
1. Add 'u' to senseor.record
2. Add 'I'and'p' to sensor.record and obtain from u = I / p.
I need All of 'I','u','p', so I thought would save memory for'p' when calculated this way.
But when I calculated using two methods, I got different answers of 'u'.
Which method is appropriate for calculating the particle velocity correctly?
I read the code, but there are various types of particle velocities, and I don't understand the difference correctly.
【various types of particle velocities】
ux_sgx(=sensor_data.ux) : 1/2 staggered shift to time and space(?)
ux_shifted(=sx_nonstaggerd) : 1/2 staggered shift in time (?)
ux_sgt : unstaggerd
ux_sgt is used to calculate the sound intensity with "kspaceFirstOrder_saveIntensity".
sensor_data(sensor_mask_index).Ix = sensor_data(sensor_mask_index).p .* ux_sgt;
Therefore, I thought that ux_sgt was unstaggered.
If it is correct, I feel that it is correct to find'u'from I / p.
Perhaps I don't understand enough. thank you.
Hi monmo,
The variable ux_sgt is the velocity NOT staggered in space, and NOT staggered in time (see e.g., line 46 in V1.3). It has to be at the same points in space and time to multiply by the pressure.
The particle velocity returned by sensor.record = {'u'} is staggered in BOTH space and time.
The partial velocity returned by sensor.record = {'u_non_staggered'} is NOT staggered in space but IS staggered in time.
Thus, the particle velocity recovered from the intensity will match u_non_staggered only after unstaggering the latter in time.
Hope that helps,
Brad.
You must log in to post.