Negative Vectors

classic Classic list List threaded Threaded
8 messages Options
monicavd74 monicavd74
Reply | Threaded
Open this post in threaded view
|

Negative Vectors

I am using PIV to estimate the tangential velocity of a fluid in an electromagnetic stirrer. This electromagnetic stirrer is an annular channel shape. I obtained as a result, positive velocities and negative velocities. I don’t know what the reason of negative velocities is. What is the algorithm or formula used by the PIV for calculating the tangential velocity?

This is an example

Distance on line [m],Tangent velocity [m/s]
0,-4.701840406e-006
4.980748751e-005,-2.292887907e-006
9.961497501e-005,-1.4783411e-006
0.0001494224625,-8.781868044e-007
0.00019922995,-3.319597275e-007
0.0002490374375,2.348581182e-007
0.000298844925,8.01675964e-007
0.0003486524126,1.36849381e-006
0.0003984599001,1.935311656e-006
0.0004482673876,2.502129501e-006
0.0004980748751,3.068947347e-006


Image Results
Thanks,

Monica
William William
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

Are you sure you want to have tangential velocity...? That are the velocity components parallel to the line. I'd guess you would want velocities perpendicular to the line?

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.

William William
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

In reply to this post by monicavd74
Tangential velocity is positive, when the velocity component is from point A towards point B, and negative when from point B towards point A.

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.

monicavd74 monicavd74
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

In reply to this post by William
Hi,
The operation of our prototype is as follows:
We analyse the steady laminar flow of an electrolyte in an open annular channel driven by an azimuthal Lorentz force. An open annular channel, limited laterally by two concentric electrically conducting cylinders and by an insulating wall at the bottom is considered. A low conductivity liquid with particles is contained in the channel, while a uniform magnetic field is applied vertically along the cylinders. A potential difference is applied between the cylindrical electrodes so that an electric current circulates radially within the fluid. The current interacts with the applied magnetic field, giving rise to a Lorentz force that drives the fluid in the azimuthal direction. When the current flows inwardly, the fluid will move in the counter-clockwise direction. Also, vortices appear at a certain voltage.

I need to calculate the maximum velocities at which the fluid moves. For that reason I tried to calculate tangential velocity with the PIV.
monicavd74 monicavd74
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

In reply to this post by William


Hello, 
            would like to contribute to update MATLAB license and keep support PIVlab, but the PAYPAL system does not allow me to make payments from my country. How can I contribute to this? Do you know another way?

2018-05-30 23:06 GMT-07:00 William [via PIVlab - Time-Resolved Digital Particle Image Velocimetry Tool for MATLAB] <[hidden email]>:
Tangential velocity is positive, when the velocity component is from point A towards point B, and negative when from point B towards point A.

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.




If you reply to this email, your message will be added to the discussion below:
http://pivlab-time-resolved-digital-particle-image-velocimetry-tool-f.33690.n7.nabble.com/Negative-Vectors-tp773p775.html
To unsubscribe from Negative Vectors, click here.
NAML

William William
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

Hi Monica, this would be very kind. Maybe you could try a normal PayPal transaction and I can put it to the Moneypool myself. The email is
T,r,a,s,h,c,a,n@g,m,x.c,o,m (remove all commas)
Thanks!

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.

monicavd74 monicavd74
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

Hi William, I sent my contribution for the PIVLab update
Cheers
Monica

2018-08-14 22:32 GMT-07:00 William [via PIVlab - Time-Resolved Digital Particle Image Velocimetry Tool for MATLAB] <[hidden email]>:
Hi Monica, this would be very kind. Maybe you could try a normal PayPal transaction and I can put it to the Moneypool myself. The email is
T,r,a,s,h,c,a,n@g,m,x.c,o,m (remove all commas)
Thanks!

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.




If you reply to this email, your message will be added to the discussion below:
http://pivlab-time-resolved-digital-particle-image-velocimetry-tool-f.33690.n7.nabble.com/Negative-Vectors-tp773p817.html
To unsubscribe from Negative Vectors, click here.
NAML

William William
Reply | Threaded
Open this post in threaded view
|

Re: Negative Vectors

Thank you!

Please consider donating for the PIVlab project:
http://paypal.me/pools/c/81Y8wBVi4y

The developer needs to update to a recent Matlab release in order to keep the project running.