CFD Validation

Computational Fluids Dynamics (CFD) is an increasingly important technique for modelling and understanding the behaviour of fluids. For example observing the flow of air over an aircraft wing. It is very computationally demanding but with the growing power of computers it is increasingly used as a more cost effective route than practical experimental rigs. In the process industries its use is growing to model and predict batch mixing, polymerisation reactions, polymer extrusion and processing and crystallisation.

However the many variables changing during a process (concentration and turbulence) and the different length scales make CFD very challenging for many processes.

While the mathematical techniques and tools for CFD are advancing rapidly the Achilles’ heel is always the validation of the computer model against the real behaviour and determining the “constants” and initial conditions of the CFD model. 

Good process measurements can help CFD developers optimise their models.  Data can also be used to validate whether a model is reliable.

Process tomography provides concentration measurements through a process volume.  This data can be used to test and validate CFD models.

In applying tomography to CFD challenges, a key aspect is the accuracy of the tomography data and the confidence levels in the CFD model.

Process tomography can be used to test and validate a wide range of CFD models, including:

• gas-liquid mixing
• solid-liquid mixing
• multi-phase flow
• packed bed reactors

Depending on the nature of the process, a variety of other offline and online different reconstruction methods can be used, including SCG (Sensitivity Conjugate Gradients) and parametric reconstruction.

Figure: Solids concentration profiles ERT & CFD

Key benefits include:

• identify regional changes in process conditions over time for comparison with CFD predictions.

• provide process information to improve CFD models.

• determine repeatability of process conditions to characterise inherent process variability.

"CFD validation and improvement to models helped research group develop sludge thickener design improvements and realise significant savings"
 

Publications:

Bolton GT, Hooper C, Mann R and Stitt EH(2004) Flow distribution and velocity measurement in a radial flow fixed bed reactor using electrical resistance Tomography, Chemical Engineering Science, Vol. 59, No. 10, pp 1989-1997

G.T. Bolton, K.M. Primrose, C. Qiu, M. Castillo del Rio, M. Wang, H.I. Schlaberg, D. Brown, J. Brown, K.C. Low, G. Padron (2009) Comparison between electrical resistance tomography, CFD and other measurementtechniques, 3rd International Workshop on Process Tomography (IWPT-3), 17-19 April 2009, Tokyo, Japan

Pakzad, L., Ein-Mozzafari, F. and Chan. P. (2008) Using electrical resistance tomography and computational fluid dynamics modelling to study the formation of cavern in the mixing of pseudoplastic fluids possessingyield stress, Chemical Engineering Science, Vol. 63, pp 2508-2522

In the press:

• Engineering Talk - January 2003 - Process Tomography validates Synetix calculations
• Chemical Engineering - March 2003 - Process Tomography validates CFD model
• Process Engineering  - March 2003 - Validate CFD with tomography

If you would like to receive a copy of an article, please contact ITS.

Register to access our "Radial flow packed bed reactor CFD validation" case study available from the Download section on the right.