Generating thrust from a momentum source in Ansys Fluent in a ducted fan

Chiara1618 · November 25, 2021, 05:33

Good morning,

I'm trying to simulate the thrust generated by a propeller in a ducted fan in Ansys Fluent. For the propose I've introduced an actuator disk inside the ducted fan and inside this disk I've put a momentum source (N/m^3).

My question is now: how can I calculate the thrust generated by the fan? And how is this related to the momentum source imposed?

Thanks

jsm · November 25, 2021, 22:42

How propeller and fan are connected? What is actuator disk? Your question is not easy to understand.

Without seeing the geometry, difficult to answer your question. Please add some images of geometry.

LuckyTran · November 26, 2021, 03:47

The volumetric momentum source (in N/m^3) integrated over the disk region is the thrust (in N). Since you impose the momentum source and decide the shape of the disk, it's just simple algebraic multiplication of the source strength and volume of the disk.

Chiara1618 · December 1, 2021, 04:45

The propeller is inside the ducted fan. Instead simulate the complex propeller I've inserted a disk in the domain (actuator disk... It's just a fluid region with no boundaries) within which I've put a momentum source

Chiara1618 · December 1, 2021, 04:47

Ok so supposing I insert a momentum source of 1000N/m^3 in a disk of volume 0.1m^3, I should expect a thrust of 100N... How do I prove I obtain this thrust??

cbooks77 · December 1, 2021, 19:28

If you are trying to get detailed results for thrust then why would you make such a big assumption to the geometry? Model the Fan blades explicitly using the MRF approach. Then integrate the forces on the blades to calculate the thrust. The MRF is not even very expensive to run.

Chiara1618 · December 2, 2021, 02:35

My final geometry is too complex to simulate also the fan. I need to proceed this way but knowing the thrust which is generated by this model

satishorion · July 10, 2024, 11:04

Hi,
Were you able to solve the thrust issue. I am also trying to do the same ducted propeller but its a complete 360 Deg model with the duct. The direct result output from the fluent for normal force on blade and the momentum approach are giving different thrust values.

Regards
Satish

Quote:

Originally Posted by Chiara1618

Good morning,

I'm trying to simulate the thrust generated by a propeller in a ducted fan in Ansys Fluent. For the propose I've introduced an actuator disk inside the ducted fan and inside this disk I've put a momentum source (N/m^3).

My question is now: how can I calculate the thrust generated by the fan? And how is this related to the momentum source imposed?

Thanks

November 25, 2021, 05:33	Generating thrust from a momentum source in Ansys Fluent in a ducted fan	#1
Chiara1618 New Member Chiara Join Date: Mar 2021 Posts: 11 Rep Power: 5	Good morning, I'm trying to simulate the thrust generated by a propeller in a ducted fan in Ansys Fluent. For the propose I've introduced an actuator disk inside the ducted fan and inside this disk I've put a momentum source (N/m^3). My question is now: how can I calculate the thrust generated by the fan? And how is this related to the momentum source imposed? Thanks

November 25, 2021, 22:42		#2
jsm Senior Member JSM Join Date: Mar 2009 Location: India Posts: 192 Rep Power: 20	How propeller and fan are connected? What is actuator disk? Your question is not easy to understand. Without seeing the geometry, difficult to answer your question. Please add some images of geometry. __________________ With regards, JSM

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November 26, 2021, 03:47		#3
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,754 Rep Power: 66	The volumetric momentum source (in N/m^3) integrated over the disk region is the thrust (in N). Since you impose the momentum source and decide the shape of the disk, it's just simple algebraic multiplication of the source strength and volume of the disk.

December 1, 2021, 04:45		#4
Chiara1618 New Member Chiara Join Date: Mar 2021 Posts: 11 Rep Power: 5	The propeller is inside the ducted fan. Instead simulate the complex propeller I've inserted a disk in the domain (actuator disk... It's just a fluid region with no boundaries) within which I've put a momentum source

December 1, 2021, 04:47		#5
Chiara1618 New Member Chiara Join Date: Mar 2021 Posts: 11 Rep Power: 5	Ok so supposing I insert a momentum source of 1000N/m^3 in a disk of volume 0.1m^3, I should expect a thrust of 100N... How do I prove I obtain this thrust??

December 1, 2021, 19:28		#6
cbooks77 New Member Chris Join Date: Mar 2021 Posts: 23 Rep Power: 5	If you are trying to get detailed results for thrust then why would you make such a big assumption to the geometry? Model the Fan blades explicitly using the MRF approach. Then integrate the forces on the blades to calculate the thrust. The MRF is not even very expensive to run.

December 2, 2021, 02:35		#7
Chiara1618 New Member Chiara Join Date: Mar 2021 Posts: 11 Rep Power: 5	My final geometry is too complex to simulate also the fan. I need to proceed this way but knowing the thrust which is generated by this model