University of Thi-Qar Journal for Engineering Sciences

Computations are presented to study the turbulent flow and heat transfer over a channel backward-facing step under impingement cooling. The problem was simulated for different parameters, such as the number of impinging jets, contraction ratio, size of jets, and jet and channel Reynolds numbers. The contraction ratio had the values 0.25, 0.35 and 0.5. The impinging jets were normal to the cross-channel flow. A control volume approach using staggered grid techniques was considered to integrate the continuity, fully elliptic Navier-Stockes and energy equations. A computer program was developed, and the SIMPLE algorithm was employed to determine the existence of coupling between the continuity and Navier-Stockes equations. The effect of turbulence was modelled using a k-ε model while the wall functions laws were used to treat the regions near the solid walls. The presented results show that the strength and size of re circulation regions near the reattachment region just after the backward-facing step increase as the contraction ratio increases. Also, the results show that the size of jets, number of jets, and jet and channel Reynolds numbers have a significant effect on the flow field, turbulent kinetic energy and variation of the Nusselt number.

In the article mathematical model for routing in the MPLS network is proposed. Also method of two-level routing on the basis of goal coordination principle in the MPLS network is offered. The method is used to increase the scalability of flow-based routing strategies.

Fluid flow through packed bed has many important applications in chemical and other process engineering fields such as fixed-catalytic reactor, adsorption of a solute, gas absorption, combustion, drying, filter bed, wastewater treatment and the flow of crude oil in petroleum reservoir.The present work presents the study of air flow through a packed bed of glass sphere packing with 0.42, 0.50, 0.61, 0.79 and 1.01 cm in diameter, and the packed column was 7.62cm in diameter and 57 cm long. Different flow rates of fluid were used which expressed by modified Reynolds number. Many variables were studied in this work such as fluid type (airflow), flow rate and the packing porosity, in order to study the effect of these variables on the friction factor.Anew correlation for friction factor as a function of Reynolds number for air flow through packed of mono size packing has been made.The results showed that the pressure drop through a packed bed is highly sensitive to the packing porosity which has a significant effect on the friction factor. It was found that as the bed porosity increases the friction factor values as well as the pressure drop values decrease.

This paper presents investigation of behavior of bentonite mudcake between soil and concrete. A number of simple shear test have been performed on sandy clay and concrete specimens with and without bentonite mudcake at contact. The constitutive relations such as stress-displacement, dilative and the strength relations have been discussed in details. It was found that thin bentonite mudcake between sandy clay and concrete increases the shear strength, the sliding between soil and concrete in addition to the vertical displacement. The bentonite mudcake has a dual reaction; the upper face interacts with soil and the lower face interacts with concrete, showing different effects.

This study investigates the effect of thermal residual stress analysis on tetrahedral elements surface structure using finite element technique. An understanding of the effects related to the thermal residual stress is necessary to improve the ability of designers to precisely predict the catastrophic behavior of the apparatuses during overhaul. Tetrahedral elements surface structure production component subjected to applied loads needs to optimize this component that is critical to the tetrahedral elements surface structure efficiency. The applied loads and resulting residual stresses under service conditions is demanded. The finite element modeling was performed. In addition, the fracture life prediction was carried out using finite element based on fatigue analysis. It was observed that the fracture was significantly influenced due to the residual stresses. The obtained result indicates that the existence residual stresses produce the shortest fatigue life for applied loads conditions. The process is one of the promising surface treatments to increase the fracture life for tetrahedral elements surface structure.

A back-propagation neural network (BPNN) model is developed to predict the punching shear strength of square ferrocement slabs. The experimental data used for training and testing the neural network model, are collected from several sources.They are arranged in a format of seven input parameters (the effective span, slab thickness, yield tensile strength of wire mesh, volume fraction of wire mesh, mortar compressive strength, width of square loaded area,boundary condition of the supported slabs) and one output parameter (punching shear strength). A parametric study is carried out using BPNN to study the influence of each parameter affecting the punching shear strength of ferrocement slabs. A comparison with the experimental results and those from other existing empirical equations demonstrates that the predictions from BPNN are indeed better. We conclude that the BPNN model may serve as a good tool for predicting the punching shear strength.

This paper gives an experimental study for the thermal conductivity of mortar concrete material by adding polystyrene (styropr) as granules for different volume percentages (0%,5% , 10% and 15 %). Polystyrene considered as a polymeric thermal isolative material. The specimens of 343 cm3 are made with a mixing percentages of 22.72% cement, 68.18% sand and 9.1% water which they accredited according to the Iraqi standardization No. (5 /1984).Tests are carried out in the laboratories of the engineering college– Karbalaa university to determine the thermal conductivity, compressive strength, porosity and the density for the specimens. The results showed that the polystyrene leads to decrease the thermal conductivity of the mortar concrete. The thermal conductivity of the (5%) polystyrene specimen is decreased by (2.6%), (10%) polystyrene specimen is decreased by (10.4%), and for the specimen of (15%) polystyrene is decreased by (20.28%).The compressive strength of the specimen is decreased by increasing the polystyrene percentages and this clearly appear in the 10% and the 15% specimens but it isn't exceed the permissible range according to the Iraqi standardization No. 5/1984 (compressive strength≥23 Mpa).

It is known that temperature rise boosts the generations of electron-holes pairs in semiconductors and increases their conductivity that obtained to increase noise.High Electron Mobility Transistors (HEMTs) gives many advantages like low noise and high associated gain at microwave frequencies.Different shapes and places in containers are done to analyze the temperature effect on chips with other thermal and aerodynamic parameters.In this paper,the performance of integrated optical receiver consisting of PIN(Positive Intrinsic Negative)-photo diode and HEMT-based transimpedance type amplifier is analyzed upon the effect of temperature variation. Variation of temperature occurs when change device space in one block covers.The simulation results show that the sensitivity (Psen) of an optical receiver is minimal in space when temperature effect is low if it is based on well-designed HEMT.