Analysis of two-equation turbulence models for recirculating flows

The two-equation kappa-epsilon model is used to analyze turbulent separated flow past a backward-facing step. It is shown that if the model constraints are modified to be consistent with the accepted energy decay rate for isotropic turbulence, the dominant features of the flow field, namely the size of the separation bubble and the streamwise component of the mean velocity, can be accurately predicted. In addition, except in the vicinity of the step, very good predictions for the turbulent shear stress, the wall pressure, and the wall shear stress are obtained. The model is also shown to provide good predictions for the turbulence intensity in the region downstream of the reattachment point. Estimated long time growth rates for the turbulent kinetic energy and dissipation rate of homogeneous shear flow are utilized to develop an optimal set of constants for the two equation kappa-epsilon model. The physical implications of the model performance are also discussed

Turbulent separated flow past a backward-facing step: A critical evaluation of two-equation turbulence models

The ability of two-equation models to accurately predict separated flows is analyzed from a combined theoretical and computational standpoint. Turbulent flow past a backward facing step is chosen as a test case in an effort to resolve the variety of conflicting results that were published during the past decade concerning the performance of two-equation models. It is found that the errors in the reported predictions of the k-epsilon model have two major origins: (1) numerical problems arising from inadequate resolution, and (2) inaccurate predictions for normal Reynolds stress differences arising from the use of an isotropic eddy viscosity. Inadequacies in near wall modelling play a substantially smaller role. Detailed calculations are presented which strongly indicate the standard k-epsilon model - when modified with an independently calibrated anisotropic eddy viscosity - can yield surprisingly good predictions for the backstep problem

Analysis of an RNG based turbulence model for separated flows

A two-equation turbulence model of the K-epsilon type was recently derived by using Renormalization Group (RNG) methods. It was later reported that this RNG based model yields substantially better predictions than the standard K-epsilon model for turbulent flow over a backward facing step - a standard test case used to benchmark the performance of turbulence models in separated flows. The improvements obtained from the RNG K-epsilon model were attributed to the better treatment of near wall turbulence effects. In contrast to these earlier claims, it is shown in this paper that the original version of the RNG K-epsilon model substantially underpredicts the reattachment point in the backstep problem. This is a deficiency that is traced to the modeling of the production of dissipation term. However, with the most recent improvements in the RNG K-epsilon model, excellent results for the backstep problem are now obtained

LIFE AND LIVELIHOOD OF KANI TRIBES IN THE WESTERN GHATS OF TAMILNADU

The Western Ghats region is the home to the Kani tribes. The Kanis also live in the Ghat regions of Tirunelveli district in Tamil Nadu. At present, there are five Kani settlements in the Kalakkad Mundanthurai Tiger Reserve (KMTR) areas of Tamilnadu. Servalar Kani settlement is the chosen study area forms part of Kalakkad Mundanthurai Tiger Reserve comes under the jurisdiction of the Tamilnadu Forest Department. Once a nomadic tribe, the community now does not migrate from one place to another.  Apart from agriculture, the Kani tribes collected honey from the forest regions and cultivated other minor forest produce. This helped them in earning some money to cater for their needs. The relationship between forests and the Kani tribe is intimate and age old. They have close association with forests and hills. Their dependency and association with forests are reflected in all aspects of their culture. They proudly identify them with forests and mountain. They live with nature. All the essential items for living are available in forest. Forests are their dwelling place. This research paper describes the strategic location and the ecological importance of the Pothigai Hills focusing on Kalakkad Mundanthurai Tiger Reserve (KMTR). And it highlights the life and livelihood of the Kani tribes in their settlement at Servalar region

Large-eddy simulations of flow and heat transfer for jet impingement on static and vibrating surfaces

The present numerical work serves to understand the flow and thermal characteristics of a turbulent impinging air jet under dynamic flow and geometric conditions using Large-eddy Simulations (LES). A clear relationship between the large-scale structures and resulting heat transfer on the impingement surface exists and was demonstrated through highly-resolved LES of both static and dynamic surface configurations

Retailer's inventory system in a two-level trade credit financing with selling price discount and partial order cancellations

In today's fast marketing over the Internet or online, many retailers want to trade at the same time and change their marketing strategy to attract more customers. Some of the customers may decide to cancel their orders partially with a retailer due to various reasons such as increase in customer's waiting time, loss of customer's goodwill on retailer's business, and attractive promotional schemes offered by other retailers. Even though there is a lag in trading and order cancellation, this paper attempts to develop the retailer's inventory model with the effect of order cancellations during advance sales period. The retailer announces a price discount program during advance sales period to promote his sales and also offers trade credit financing during the sales periods. The retailer availing trade credit period from his supplier offers a permissible delay period to his customers. The customer who gets an item is allowed to pay on or before the permissible delay period which is accounted from the buying time rather than from the start period of inventory sales. This accounts for significant changes in the calculations of interest payable and interest earned by the retailer. The retailer's total cost is minimized so as to find out the optimal replenishment cycle time and price discount policies through a solution procedure. The results derived in mathematical theorems are implemented in numerical examples, and sensitivity analyses on several inventory parameters are obtained

Application of a new K-tau model to near wall turbulent flows

A recently developed K-tau model for near wall turbulent flows is applied to two severe test cases. The turbulent flows considered include the incompressible flat plate boundary layer with the adverse pressure gradients and incompressible flow past a backward facing step. Calculations are performed for this two-equation model using an anisotropic as well as isotropic eddy-viscosity. The model predictions are shown to compare quite favorably with experimental data

KANI TRIBES’ KNOWLEDGE ABOUT INDIGENOUS MEDICINAL PLANTS IN THE POTHIGAI HILLS OF TAMILNADU

All over the world the hills are inhabited by tribes. Nestled in the tropical forests located mainly in the southernmost part of the Western Ghats, India, inhabit an indigenous Kani tribe traditionally nomadic. They are the original inhabitants residing in the dense forest from time immemorial. They are the one of the oldest surviving hunter-gatherer tribes in the world. The indigenous Kani tribes in the Pothigai Hills in Tamilnadu and their living environment are enriched with indigenous knowledge resources. These tribes have a rooted traditional and indigenous knowledge about medicinal plants. Yet, all their knowledge is gradually disappearing due to many reasons. This study has great significance in the collection of that knowledge, preparation of recorded data and conservation of that information for the use of future generation. Since their knowledge system is embedded, collective and diversified the ownership, protection and management of these areas are complicated. The collection of information, classification, copyright, intellectual property rights, the politics involved etc are the other problems involved. So far these resources are not yet systematically documented and scientifically analyzed. Hence this study aims to overcome the above said problems. &nbsp