Toward the large-eddy simulation over a hypersonic elliptical cross-section cone

2000 ◽  
Author(s):  
M. Martin ◽  
Heath Johnson ◽  
Ioannis Nompelis ◽  
Graham Candler ◽  
Greg Weirs ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Cross Section ◽  
Elliptical Cross Section ◽  
Elliptical Cross ◽  
Eddy Simulation ◽  
Large Eddy

Large Eddy Simulation in a Duct With Rounded Skewed Ribs

2005 ◽  
Author(s):  
Aroon K. Viswanathan ◽  
Danesh K. Tafti
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Cross Section ◽  
Mean Flow ◽  
Cross Sectional ◽  
Square Duct ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Mean ◽  
Experimental Values

Results from Large Eddy Simulation (LES) of fully developed flow in a ribbed duct are presented with rib pitch-to-height ratio (P/e) is 10 and a rib height to hydraulic diameter ratio (e/Dh) is 0.1. Computations are carried out on a square duct with 45° ribs on the top and bottom walls arranged in a staggered fashion. The ribs have a rounded cross-section and are skewed at 45° to the main flow. The Reynolds number based on bulk velocity is 25,000. Mean flow and turbulent quantities, together with heat transfer and friction augmentation results are presented for a stationary case. The flow is characterized by a helical vortex behind each rib and a complementary cross-sectional secondary flow, both of which result from the angle of the rib with respect to the mean flow and result in a spanwise variation of the heat transfer. The mean flow, the turbulent quantities and the heat transfer in the duct show similar trends as in the duct with square cross-section ribs. However the results show that there is lesser friction in the ducts with rounded ribs. The overall heat transfer on the ribbed wall was augmented by 2.85 times that of a smooth duct, at the cost of friction which increases by a factor of 10. The computed values compare well with the experimental values.

scholarly journals Research on heat transfer characteristics of fractal-generated turbulence based on large eddy simulation

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 3993-4004
Author(s):  
Chengdong Duan ◽  
Yuncong Jiang ◽  
Nannan Wu ◽  
Qiwen Xu ◽  
Lijun Wang
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Cross Section ◽  
Mesh Size ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Effective Mesh Size ◽  
Layer Region

Turbulence plays an important role in the fields of heat and mass transfer and enhanced chemical reaction. In order to explore the effect of grid-generated turbulence on flow heat transfer, in this paper, three different fractal grid structures with the same blocking ratio ?, effective mesh size Meff and thickness ratio tr= t max/t min (Case1: The grid cross-section is a triangle, Case2: the grid cross-section is an inverted triangle, Case3:the grid cross-section is square, Case4:no grid) and without the grid were simulated based on large eddy simulation. The aim of this simulation is to explain the evolution characteristics and heat transfer mechanism of turbulent flow field under the four cases. The results show that, in the same initial condition, Case 2 can generate the highest turbulence intensity and the feature of heat transfer on the cylindrical surface is more uniform. In Case 3, the boundary-layer in the flow field is separated earlier, and more vortices are excited to enhance the heat transfer than other cases in the boundary-layer region. The surface average Nusselt number is 1.3 times than that of Case 4.

Large Eddy Simulation of the Anti-Erosion Characteristics of the Ribbed-Bend in Gas-Solid Flows

2004 ◽  
Vol 126 (3) ◽  
pp. 672-679 ◽  
Author(s):  
J. R. Fan ◽  
K. Luo ◽  
X. Y. Zhang ◽  
K. C. Cen
Keyword(s):  
Large Eddy Simulation ◽  
Cross Section ◽  
Erosion Rate ◽  
Isosceles Triangle ◽  
Impact Angle ◽  
Particle Impact ◽  
Erosion Rates ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Erosion Efficiency

In order to find out the ribs with the best anti-erosion efficiency, the erosion effects in three 90° duct bend gas-solid flows with different ribs are investigated and compared with that in the bare bend. Three different kinds of ribs are studied, which have square cross section, isosceles right-angled triangle shape cross section and isosceles triangle shape cross section, respectively. The arrangement and the geometry dimensions of the ribs are the same. The gas phase flow field is solved by the large eddy simulation technique considering the interaction between the gas and the particles, whereas the particles are tracked by Lagrangian method. The results exhibit that the erosion rates of all the ribbed bends are greatly reduced due to the adding of the ribs compared with that of the bare bend. Among the three different kinds of ribs, the isosceles right-angled triangle ribs have the highest anti-erosion ability. The reason is that the particle impact velocity on the walls in the isosceles right-angled triangle ribbed bends is decreased to the utmost and the corresponding particle impact angle is altered adequately due to the special shape of the ribs. In addition, the rib erosion rate, the sidewall erosion rate and the bend wall erosion rate are calculated separately. It is found that the rib erosion rate is half of the wall erosion rate, and the sidewall erosion rate is so low that it can be omitted compared with the bend wall erosion rate.

Sign in / Sign up

Export Citation Format

Share Document