Papers by Mohammed H A S H I M Siddig
Fluid Mechanics Textbook (in Arabic), 2010
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The importance of this study arises from the nature of the Sudanese crude which contains wax. The... more The importance of this study arises from the nature of the Sudanese crude which contains wax. The crude gels when the line is shutdown for any reason. To restart a pipeline filled with the waxy crude oil, a sufficient pressure must be applied to break the gel and restart the flow. This research was conducted on Greater Nile Petroleum Operating Company (GNPOC) crude oil which represents one of the main crudes in Sudanese oil export. It has essentially aimed at studying the effects of thermal and chemical treatments on the process of pipeline restarting with emphasis on two major factors: the yield stress and the pour point. The experimental work was completed in five stages; two for the thermal treatment and three for the chemical treatment followed by analysis of the results obtained. The study succeeded in determining a temperature range for the thermal treatment and a temperature range at which PPD should be added for chemical treatment. Also the study determines the suitable PPD ...
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University of Khartoum Engineering Journal, 2012
The Restartability of the Sudanese Nile Blend crude oil inside Test Loop pipeline was performed t... more The Restartability of the Sudanese Nile Blend crude oil inside Test Loop pipeline was performed to understand the parameters determining the yield stress and describe the process of yielding up to final line clearing. Test Loop is designed to find the relationship between the required restart time and the pressure required and also to find the blend yield stress. The yield stress of the Nile Blend was found to be affected significantly by the shutdown time, static cooling rate after shutdown, and the final temperature after shutdown
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Solar Energy
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Wind Engineering
A study on the optimal matching of centrifugal pumps and large-scale wind turbines is reported. T... more A study on the optimal matching of centrifugal pumps and large-scale wind turbines is reported. The study includes mathematical modelling of the performance of high-capacity centrifugal pumps when matched with efficient high-speed low-solidity wind turbines. The dependence of the performance of wind pumps on the dimensionless parameter v/√( gh), termed the wind pump’s Froude number, was fully analysed. Similar to earlier reported results on wind-powered piston pumps, analysis is showing that the wind pump’s Froude number is the dominant independent dimensionless parameter that fully defines the system’s performance. Operation with continuous variable transmission was analysed and shown to optimize the wind pump’s performance, particularly at medium and low wind speeds. The optimum relation between the required gearbox transmission ratio and Froude number of a wind-powered centrifugal pump was analytically established for three different pumps. In addition to continuous variable tran...
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Journal of Mechanical Engineering Science
A DISA two-colour back-scatter laser Doppler anemometer was used to take measurements of mean and... more A DISA two-colour back-scatter laser Doppler anemometer was used to take measurements of mean and fluctuating velocities of an air flow of 4.6 × 104 Reynolds number in a short duct with a normal wall fixed to one side. Walls of 30 and 20 mm height were investigated and the resulting flow patterns were compared.
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Wind Engineering, Feb 19, 2015
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Khartoum University Engineering Journal, Nov 19, 2012
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The design of an efficient current-driven pump is outlined. The pump tested on the river Nile nea... more The design of an efficient current-driven pump is outlined. The pump tested on the river Nile near Khartoum, is shown to be capable of matching the needs of typical river Nile farms of areas less than one hectare at worst river level seasons.
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The over all cost of using a wind pump - or a number of wind pumps - for a watering duty HQ is es... more The over all cost of using a wind pump - or a number of wind pumps - for a watering duty HQ is estimated and compared to the cost of using a diesel pump for a similar duty. To reduce cost to a present value the discount rate is estimated using a technique depending on real local options of farmers rather than conventional costing techniques. The study revealed a clear viability of wind pumps use for average wind speeds 5m/s and above. And a clear inadequacy of wind pumping for speeds of 3m/s and below. In between these limits viability depends on the local fuel-price-index.
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The hydraulic and thermal features of the flow in the 1500 km long pipeline of Sudan's newly ... more The hydraulic and thermal features of the flow in the 1500 km long pipeline of Sudan's newly exploited oil are analyzed. The mathematical model of the resulting simulator software Nift is described. The simulator is shown to predict flow parameters for normal oil transport conditions. Comparison of the simulator's results to actual operational conditions reflected good agreement.
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The importance of this study arises from the nature of the Sudanese crude which contains wax. The... more The importance of this study arises from the nature of the Sudanese crude which contains wax. The crude gels when the line is shutdown for any reason. To restart a pipeline filled with the waxy crude oil, a sufficient pressure must be applied to break the gel and restart the flow. This research was conducted on Greater Nile Petroleum Operating Company (GNPOC) crude oil which represents one of the main crudes in Sudanese oil export. It has essentially aimed at studying the effects of thermal and chemical treatments on the process of pipeline restarting with emphasis on two major factors: the yield stress and the pour point. The experimental work was completed in five stages; two for the thermal treatment and three for the chemical treatment followed by analysis of the results obtained. The study succeeded in determining a temperature range for the thermal treatment and a temperature range at which PPD should be added for chemical treatment. Also the study determines the suitable PPD ...
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تقترح الدراسة قيمة مكافئة لما يعرف بمعدل الفائدة، ممبنية على الخيارات الفعلية للمزارع السوداني. و... more تقترح الدراسة قيمة مكافئة لما يعرف بمعدل الفائدة، ممبنية على الخيارات الفعلية للمزارع السوداني. و استخدمت القيمة الناتجة هنا لمقارنة تكاليف استخدام كل من المضخات الرياحية و مضخات الديزل في المزارع الصغيرة و التوسطة. تخلص الدراسة الى جدوى استخدام الرياح في معظم أنحاء القطر برغم علو معدل الفائدة المستخدم.
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The goal of this study revolves around the use COMSOL computer program to simulate blood flow in ... more The goal of this study revolves around the use COMSOL computer program to simulate blood flow in the blood circulation of man in health and disease conditions. This is to help in appropriate decision-making for both pathological and health conditions. The study simulated blood vessels with rigid thin tubes to obtain estimates on the factors affecting the process of blood flow through the portal vein as an example of blood vessels pontifically viable for getting clogged. Accordingly, this study addressed blood flow within the portal vein in the case of a blockage and in absence of an obstruction to simulate conditions and situations on patients with liver disease and/or blood pressure. The impact of both cases to blood flow has been assessed. The results indicated the existence of substantial differences between the two models with respect to rates of velocity, pressure, strain and shear stress for the blood pressure model in the portal vein in a liver patient. The simulation conduct...
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Papers by Mohammed H A S H I M Siddig