Print ISSN: 1813-162X

Online ISSN: 2312-7589

Issue 3,

Issue 3


Computational Fluid Dynamics Modeling of Flow over Stepped Spillway

Raad Hoobi Irzooki; Jowhar Rasheed Mohammed; Afnan Salah Ameen

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 1-11
DOI:

In present paper, the computational fluid dynamics (CFD- program Flow-3D) was used to analyze and study the characteristics of flow energy dissipation over stepped spillways. Three different spillway heights (Ps) (15, 20 and 25cm) were used. For each one of these models, three numbers of steps (N) (5, 10 and 25) and three spillway slopes (S) (0.5, 1 and 1.25) were used. Eight different discharges ranging (600-8500cm³/s) were passed over each one of these models, therefore the total runs of this study are 216. The energy dissipation over these models and the pressure distribution on the horizontal and vertical step faces over some models were studied. For verification purpose of the (CFD) program, the experimental work was conducted on four models of stepped spillway and five different discharges were passed over each model. The magnitude of dissipated energy on models was compared with results of numerical program under same conditions. The comparison showed good agreement between them with standard percentage error ranging between (-2.01 - 11.13%). Thus, the program Flow-3D is a reasonable numerical program which can be used in this study. Results showed that the energy dissipation increases with increased spillway height and decreased number of steps and spillway slope. Also, the energy dissipation decreases with increasing the flow rate. An empirical equation for measuring the energy dissipation was derived
using the dimensional analysis. The coefficient of determination of this equation (R^2) equals 0.766.

Kinetic Energy Dissipation on Labyrinth Configuration Stepped Spillway

Jaafar S. Maatooq

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 12-24
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In present work a labyrinth (zigzag), in shape has been used to configure the steps of stepped spillway by using the physical model. This configuration does not introduce previously by investigators or in construction techniques of dams or cascades. It would be expected to improve the flow over chute. A magnifying the width path of each step to become, L T, instead of, W, will induce the interlocking between the mainstream and that spread laterally due to labyrinth path. This phenomenon leads to reduce the jet velocities near the surfaces, thus minimizing the ability of
cavitation and with increasing a circulation regions the ability of air entrainment be maximized. The results were encouraging, (e.g., the reverse performance has recorded for spillway slope). From the evaluation of outcome, the average recorded of percentage profits of kinetic energy dissipation with a labyrinth shape compared with the results of traditional shape were ranged between (13- 44%).
Different predictive formulas have been proposed based on iteration analysis, can be
recommended for evaluation and design.

CFD Simulation of Air Cyclone Separator

Nuha wathq Nema; Saad Nahi Saleh; Fayadh Mohamed Abed

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 25-36
DOI:

A computational fluid dynamics model was developed for air cyclone separator in order to predict the flow pattern inside the cyclone using an Eulerian approach, three dimensions Reynolds Average Navier-Stokes equations, closed via the Reynolds Stress model as a turbulence model for air flow. The particles were modeled as a discrete phase model using the Lagrangian transport model with turbulent particle dispersion. Computational fluid dynamics modeling was employed to investigate fluid flow patterns and particle trajectories at steady state operating conditions of Stairmand cyclone. Analysis of a computational fluid dynamics simulation accurately revealed that
the air flow behavior in cyclone separator consists of two vortexes : an outer vortex with a downwardly directed axial flow and an inner vortex with an upwardly directed flow, this f low profile known as Rankine vortex. A low-pressure zone appeared in the center line of the cyclone due to high swirling velocity. The results showed that the pressure drop increased with increasing the inlet air velocity. The results of the collection efficiency showed that the efficiency increased as the particles diameter increased. A good agreement achieved between the simulation results and published experimental results. The computational fluid dynamics code (ANSYS FLUENT 14.5) with
the Reynolds Stress model as the turbulence model, predicted very well the flow field parameters of cyclones and can be used in cyclone design for any dimensions.

Performance Prediction of Internal Compression Supersonic Air Intake at Range of Mach Numbers (1.1-1.5)

Hasson Shaban Hamood

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 37-46
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In this research a numerical investigation on a supersonic air intake was done. The aim of this work is to investigate a variable geometry of cross-section area for supersonic air intake at range (1.1-1.5) Mach number, to get a maximum pressure recovery. In this work, the flow starts with a normal shock attached to the intake cowl lip. The flow is assumed compressible, inviscid, twodimensional flow, unsteady, and axisymmetric. The equations (Continuity, Momentum, and Energy) were solved based on a finite volume method. The governing equations were solved iteratively using time marching technique. This part is analyzed for several Mach numbers, where the flow properties are determined from inlet of air intake to the diffuser exit. Results show that, the implementation of time marching scheme has succeeded in the prediction of the choked flow region, which is important in the study of the performance of convergent-divergent diffuser. Also the results indicated the absolute velocity increases along the convergent part and then start to decrease along divergent part independently on the values of free-stream Mach numbers.

Effect of using Windows Waste Glass as Fine Aggregate on some Properties of Concrete

Abdelmaseeh Bakos Keryou; Gailan Jibrael Ibrahim

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 47-54
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The main goal of this study is to investigate the effect of using waste glass (WG) on some mechanical properties of concrete at both fresh and hardened stages. In our study, we used local windows waste glass (WG) as partial replacement of fine aggregates with 0, 20, 25, and 30% percentages (by weight). The experimental results obtained from testing specimens prepared from concrete mixes with water/cement ratio equal to 0.5, showed that the optimum percentage of fine waste glass to be used within the concrete mix was 20%. At this percentage of replacement the compressive strength obtained at 28-days age was 39 MPa compared with 30.32 MPa for reference concrete mix.

Sensorless Speed/ Torque Control of DC Machine using Artificial Neural Network Technique

Rakan K. Antar; Ahmed A. Allu

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 55-62
DOI:

In this paper, Artificial Neural Network (ANN) technique is implemented to improve speed and torque control of a separately excited DC machine drive. The speed and torque sensorless scheme based on ANN is estimated adaptively. The proposed controller is designed to estimate rotor speed and mechanical load torque as a Model Reference Adaptive System (MRAS) method for DC machine. The DC drive system consists of four quadrant DC/DC chopper with MOSFET transistors, ANN, logic gates and routing circuits. The DC drive circuit is designed, evaluated and modeled by Matlab/Simulink in the forward and reverse operation modes as a motor and generator, respectively. The DC drive system is simulated at different speed values (±1200 rpm) and mechanical torque (±7 N.m) in steady state and dynamic conditions. The simulation results illustrate the effectiveness of the proposed controller without speed or torque sensors.

An Experimental Study of Circular Cutout Hole effect of Kevlar/epoxy-Al2O3 Composite under Subjected to Quasi-Static Compressive and Tensile Loading

Ayad Abed Ramadhan

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 63-70
DOI:

This paper has presented an experimental study of quasi-static compressive and tensile loading of cutout hole specimens of Kevlar-29/epoxy-Al2O3 laminated composite. The experimental procedure has
been developed to study the performance of (50%, 55% and 60%) volume fraction (vf) and (0o/90o and +45o/-45o) fiber orientation angle effects of these composites under quasi-static tensile and compressive
load using a servo-hydraulic testing machine. The study was concluded that the ultimate load capacity increases as volume fraction increases in tensile test. While, the maximum load bearing capacity increases
with the decrease of volume fraction in compression test. Hence, from the results obtained it can have considered the 55% volume fraction of composite panels is a good value for tensile and compression
applications.

Secured Watermarking Image Using Spread Spectrum

Abdulkareem Mohammed Salih

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 71-78
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Due to the increased development in technique of data transfer over internet and transmission media, the access and copy to these data in unathentical manner became a big challenge in the transmission media. This challenge led to make effort in digital multimedia security. In this paper a new algorithm is proposed to protect image from unauthentication access using watermarking. The watermarking algorithm hide the mark image in frequency domain using Discrete Cosine Transform and extract it at the receiver from the transmitted image without need for origin image. The basic principle of the algorithm is depend on spread spectrum commun ications. The spread spectrum depend on transmit a narrow band signal over a much larger bandwidth where that the signal energy is undetectable. Similarly, the watermark image bits are spread by a large factor called chip-rate so that it is imperceptible and arrange in cover image in away where if the half of the watermarked image is cropped, the watermark image is not affected. The proposed algorithm efficiency is measured by using many of measurement factors such as Peak Signal to Noise Ratio PSNR and Normalized Correlation Coefficient NC, the watermark robustness and feasibility are measured by using many types of attacks.

Effect of Intermediate Sheet Piles in Non-Homogenous Soil on Seepage Properties under Hydraulic Structure using SEEP/W Program

Asmaa Abdul Jabbar Jamel

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 79-90
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The seepage through a permeable soil under hydraulic structure exerts uplift pressure and may carry soil particles there by leads to piping. This paper concerns to study the effect of using intermediate sheet pile under the apron of hydraulic structure besides the upstream and downstream piles rest on non-homogeneous soil layer. This configuration aim to show how it affect the uplift pressure, exit gradient and seepage discharge at toe of hydraulic structure by using computer program SEEP/W Package. From the software test carried out two cases, first case using two sheet pile one at the upstream and the other at the downstream, then compare its results with the second case when the sheet pile at upstream, downstream and intermediate pile introduced. Also for each run the quantity of uplift pressure, exit gradient and discharge at toe of hydraulic structure were determined to develop an empirical equations. Also, the results have been verify with artificial neural network (ANN), this verification shown good agreement between them.

Real Time Speed Control of DC Motor by Programming the Fuzzy Controller in C Language

Abdelelah K. M; Abdulaleem Abdul Fatah

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 91-95
DOI:

The fuzzy controller is one of the intelligent soft computing methods that realize a human being hierarchy sense and expert by building the program that realized it. In this work real time implementation of a fuzzy controller is realized by programming the industrial computer in c++ language. The performed fuzzy controller has two inputs and one output. The inputs are the speed error and change in error with controller output as PWM. The applied program architecture uses the matrix representation and subroutines for data entering the linguistic memberships for both error
and change in error and performing rule-base in the inference mechanism using fuzzy logic. The output of the defuzification is pulse width modulation to the chopper drive circuit. The result shows good a fulfillment of the soft computing of the controller and with fast response and the effect of load as a disturbance on the shaft of the motor has been rejected quickly.

Acidic Attack Resistance of Cement Mortar Treated with Alkaline

Nadia Nazhat Sabeeh

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 96-104
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The negative effect of acidic attack on the properties of concrete and cement mortar is a topic of increasing significance in the recent years. Many attempts has occurred to mitigate this negative impact by improving the properties of concrete and increase resistance to acids by using additives. The present study includes treatment of sand by alkaline material and examine the effect of treatment on cement mortar resistance towards hydrochloric and sulfuric acid. Results show that sand treatment by alkaline material significantly enhance mortar ability to resist acids. In terms of
loss weight, the maximum weight rate gain was 25.54% for specimens immersed in Hydrochloric acid with water cement ratio 40%. For specimens immersed in HCl, the average gain in compressive strength is (20.15-19.433)% for w/c (40-45)% respectively. The average gain in modulus of rupture toward the influence of H2SO4 is (18.37–17.99)% for w/c (40-45)%, respectively.

Optimization of Eye Diagram Based on Adaptive Decision Feedback Equalizer for High Speed Digital System

Amenah. I. Kanaan

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 105-115
DOI:

Eye diagram used in a lot of radio and telecommunication application, but it can also be used in digital signal integrity. This kind of analysis is a common indicator of performance in digital transmission systems. As integration density and data rates increase, dispersive losses, reflections and crosstalk can severely degrade signal integrity. Fortunately, these effects are linear processes. Accordingly, simple, on-chip signal processing techniques can compensate for them. In this paper we introduce an approach to improve eye diagram for data transmission that indicate the signal strength by using adaptive Decision Feedback Equalizer (DFE) in receiver circuits of digital system. The simulation results are presented to validate the efficiency of the proposed method.

Optimization of Eye Diagram Based on Adaptive Decision Feedback Equalizer for High Speed Digital System

Amenah. I. Kanaan

Tikrit Journal of Engineering Sciences, Volume 23, Issue 3, Pages 105-115
DOI:

Eye diagram used in a lot of radio and telecommunication application, but it can also be used in digital signal integrity. This kind of analysis is a common indicator of performance in digital transmission systems. As integration density and data rates increase, dispersive losses, reflections and crosstalk can severely degrade signal integrity. Fortunately, these effects are linear processes. Accordingly, simple, on-chip signal processing techniques can compensate for them. In this paper we introduce an approach to improve eye diagram for data transmission that indicate the signal strength by using adaptive Decision Feedback Equalizer (DFE) in receiver circuits of digital system. The simulation results are presented to validate the efficiency of the proposed method.