UFR 4-18 Description: Difference between revisions
| Line 18: | Line 18: | ||
The pin fins accelerate the flow in the reduced passages and produce wake regions behind the pins caracterized by strong vortex shedding. This leads to high turbulence levels which enhance heat transfer. The presence of endwalls leads to the apparition of horseshoe vortices which alse enhances heat transfer. | The pin fins accelerate the flow in the reduced passages and produce wake regions behind the pins caracterized by strong vortex shedding. This leads to high turbulence levels which enhance heat transfer. The presence of endwalls leads to the apparition of horseshoe vortices which alse enhances heat transfer. | ||
Finally, the available heat transfer measurements by Ames et al. (2004, 2005, 2006, 2007), which will be used all along this UFR, are rare and valuable for CFD validation. The present case can be qualified as a semi-industrial test-case as it has a complex physics but its geomhetry in enough simple to allow deep and precise analysis. | Finally, the available heat transfer measurements by Ames et al. (2004, 2005, 2006, 2007), which will be used all along this UFR, are rare and valuable for CFD validation. The present case can be qualified as a semi-industrial test-case as it has a complex physics but its geomhetry in enough simple to allow deep and precise analysis. | ||
Revision as of 05:17, 19 May 2015
Flow and heat transfer in a pin-fin array
Confined Flows
Underlying Flow Regime 4-18
Description
Here some information about the objectives for investigating the flow in a pin-fin array and an overview about the works relevant to this flow are given.
Introduction
The present case consists in the flow through a wall bounded pin matrix in a staggered arrangement with a heated bottom wall. In addition to its interest for the complex underlying physics, this case is close to several industrial configurations for internal cooling of gas-turbine blades, electronic devices and can be also found in the nuclear field.
The pin fins accelerate the flow in the reduced passages and produce wake regions behind the pins caracterized by strong vortex shedding. This leads to high turbulence levels which enhance heat transfer. The presence of endwalls leads to the apparition of horseshoe vortices which alse enhances heat transfer.
Finally, the available heat transfer measurements by Ames et al. (2004, 2005, 2006, 2007), which will be used all along this UFR, are rare and valuable for CFD validation. The present case can be qualified as a semi-industrial test-case as it has a complex physics but its geomhetry in enough simple to allow deep and precise analysis.
Review of UFR studies and choice of test case
Provide a brief review of past studies of this UFR which have included test case comparisons of experimental measurements with CFD results. Identify your chosen study (or studies) on which the document will focus. State the test-case underlying the study and briefly explain how well this represents the UFR? Give reasons for this choice (e.g a well constructed test case, a recognised international comparison exercise, accurate measurements, good quality control, a rich variety of turbulence or physical models assessed etc.) . If possible, the study should be taken from established data bases. Indicate whether of not the experiments have been designed for the purpose of CFD validation (desirable but not mandatory)?
Here some information about the objectives for investigating the flow in a pin-fin array and an overview about the works relevant to this flow are given.
Relevent studies
The present configuration has been studied in the framework of the 15th ERCOFTAC-SIG15/IAHR Workshop on Refined Turbulence Modelling which took place in 2011 at EDF Chatou, France.
Experimental investigations
Several experiment exist in the literature around the use of pin fin arrays to increase the turbulence levels which leads to enhance heat transfer. One recalls here the experiments and computations which are directly related to the present configuration. The reader can refer to the two following articles to have additional references: Lawson et al. (2011) and Rao et al. (2012).
Ames et al. (2004, 2005, 2006, 2007) from University of North Dakota published several articles around the present test-case. Almost all the data which will be used to confront CFD computations are from this team except the correlations for pressure drop coefficients and Nusselt numbers provided by
Numerical investigations
This configuration has already been studied numerically by Delibra et al. [10], [11] using Unsteady Reynolds Average Navier Stokes (URANS) with the �-f model [10], [14] and hybrid Reynolds Average Navier Stokes/Large Eddy Simulation (hybrid RANS/LES) [11] for the two highest Reynolds numbers. They concluded that the URANS approach presented several discrepancies, among them, its inability to reproduce the unsteadiness of the flow around the first three arrays of the matrix. They also suggested that the small structures unresolved by URANS need to be predicted. This brought them to conduct hybrid RANS/LES (LES using a dynamic Smagorinsky model with RANS wall-treatment based on the �-f model [11]). They found that hybrid RANS/LES gave more acceptable accuracy than URANS in particular for capturing the large convective structures. Note that the computational domain of the URANS and hybrid RANS/LES approaches consisted of 8 by 2 and 8 by 1 pins, respectively, and that the wall temperature and not the heat flux was fixed.
© copyright ERCOFTAC 2024