# How to calculate centerbody thrust of an aerospike nozzle in Fluent

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 July 29, 2018, 15:47 How to calculate centerbody thrust of an aerospike nozzle in Fluent #1 Senior Member   Join Date: Sep 2017 Posts: 130 Rep Power: 7 Fellas, I'm trying to calculate the thrust of an Aerospike nozzle using fluent but I don't know how to calculate the thrust of centerbody. I've found three kinds of equations to calculate the centerbody thrust. here are the links the source of calculating thr thrust: https://www.researchgate.net/publica...whcqOzQhKJKivQ (see equation 5 for centerbody thrust) https://www.researchgate.net/publica...rospike_Nozzle (equation 15 for centerbody thrust) http://www.aerospaceweb.org/design/a...dynamics.shtml In these three sources, there are three kinds of calculating the centerbody thrust as you can see. How can I get an integral for calculating this equation in Fluent? I think we can do it using "integral surface" in fluent but it doesn't calculate "Pcenterbody-Pambint". Any idea?

 July 30, 2018, 00:55 #2 Senior Member   Alexander Join Date: Apr 2013 Posts: 2,255 Rep Power: 32 you may take a look into Custom Field Function Calculator tool in fluent (user-defined -> custom..) However, depending on what do you mean under Pambient (is it constant everywhere or not), implementation may become difficult best regards Roh likes this.

 July 30, 2018, 03:06 #3 Senior Member   Join Date: Sep 2017 Posts: 130 Rep Power: 7 Thank you Yeah, Pambient is constant, everywhere.

July 30, 2018, 03:26
#4
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Alexander
Join Date: Apr 2013
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Quote:
 Originally Posted by Roh Thank you Yeah, Pambient is constant, everywhere.
in that case go to custom field function and define there you custom variable
I think you should get something like this
Code:
`face-area-magnitude * (p - 101315)`
where 101315 is Pambient

than go to Report -> surface integrals -> select there are-weight average value ( under report type) and your new custom field function (under filed variable), select nozzle surface

best regards

July 30, 2018, 11:03
#5
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Thank you
Here is a screenshot of my Aerospike nozzle:

There is a line for sampling and averaging velocity and mass flow and pressure.

Totally I'm confused that how to calculate the total thrust. I've several source of calculating the total thrust. here is the links of total thrust and it's sources.

https://arc.aiaa.org/doi/10.2514/1.40302

https://www.researchgate.net/publica...rospike_Nozzle

https://www.researchgate.net/publica...whcqOzQhKJKivQ

IMO the correct relation for calculating the total thrust is this:

If we assume that this is our Aerospike nozzle:

Am I right? and due to this link, "Area weighted average" and "Integral" are written in this way, respectivly:

and

So, don't you think we have to use "Integral" instead of "Area weighted average"? Ok, I need to add Cos(tetha) to the right hand side of the above equation and to the tetha. How can I do this?
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 February 21, 2022, 12:30 #6 New Member   Tim Dorau Join Date: Mar 2019 Posts: 11 Rep Power: 5 Hey I know this thread is old, but did you ever find an answer here? I would be quite interested!