Papers by Keyword: Turbulent

Abstract: Monosodium Glutamate (MSG) [1] was invented more than 100 years ago from its first invention in 1908 by Japanese biochemist Kikunae Ikeda, who was trying to isolate and duplicate the savory taste of kombu, an edible seaweed used as a base for many Japanese soups. From 2016, most MSG worldwide is produced by bacterial fermentation in a process similar to making vinegar or yogurt. Sodium is added later, for neutralization. During fermentation, Corynebacterium species, cultured with ammonia and carbohydrates from sugar beets, sugarcane, tapioca (cassava tuber) or molasses, excrete amino acids into a culture broth from which L-glutamate is isolated. In this process, Monosodium Glutamate companies buy cassava [2] pulps from farmers that contain a lot of sand and impurities. In order to increase the productivity with lowest expense, the filtration of sand and solid impurities’ is performed by separation cyclone. In this paper, we study all the measure to design a system of effective pump, cyclone to extract as much as possible all of solid impurities included sand out of cassava slurry before providing to the bacterial fermentation in a process.

Abstract: This work studied the turbulent flow of the nutrient solution which affected the growth of plants in four hydroponic systems; the horizontal (traditional), the vertical cup-grown, the ladder and the droplet systems, which were connected with individual solution pumps which submerged in only one nutrient solution tank to supply the turbulent nutrient solution flow to all systems. Two experiments were done by planting Red Oak lettuce, fluid and ambient temperatures, fluid pH and sunlight intensity were measured 2 times a day from 4 systems placed in the same area and environment during 20 days of the experimental periods. From both result sets, the lower ambient and solution temperatures in the 2^nd experiment yielded more productivity. The results also showed that adjusting pipe and hose sizes did not cause the nutrient solution overflow out of the systems, the turbulent flow occurred and the horizontal system could produce the highest productivity. However, the higher pump power was required to produce the turbulent solution, the higher pump power higher heat transfer from the pump to the nutrient solution in the tank since all pumps were placed in the same solution tank, this heated solution caused the lower productivity in this work.

Abstract: This paper presents results obtained from the application of a computational fluid dynamics (CFD) code Fluent 6.3 to modelling of temperature in propane flames with air preheat. The study focuses on investigating the effect of air preheat temperature on the temperature of the flame. A standard k-ε turbulence model in combination with the Probability Density Function (PDF) model for Non Premix Combustion model and Eddy Dissipation Model (EDM) are utilized to represent the flow and temperature fields of the flame being investigated, respectively. The results of calculations are compared with experimental data of propane flame taken from literature. The results of the study showed that the combination of the standard k-ε turbulence model and PDF model is more capable of producing reasonable predictions of temperature, particularly in axial profile and rich fuel area of all two flames compared with those of EDM model. Both experimental works and numerical simulation showed that increasing the temperature of the combustion air significantly increases the flame temperature.

Abstract: A coolant mixing investigation in a head of a half-size model of VVER-440 fuel assembly (simulator) has been performed at KFKI. The PIV and PLIF measurements have been done under a selected list of power distribution options, flow rates and powers. The experiments were focused on obtaining a data for investigating the trends in temperature difference between the value registered by a thermocouple and that obtained using PLIF technique. The coolant temperature distribution has been measured in many positions along the coolant trajectory and where coolant flow leaves the rod bundle and in the cross section location of thermocouple, thus the dynamics of effect of mixing process is also declared. PIV and LPIF results show their ability to verify the primary results of CFD calculations.

Abstract: The presence of carbon dioxide (CO₂) and water in the fluid can cause severe internal corrosion in the pipelines. This study aims to observe corrosion behavior during the changes in flow rate and acidity conditions in order to obtain the relationship between the parameters by the measured corrosion rate. Corrosion rate measurements were performed for API 5L X52 steel material by using polarization method in 3.5% NaCl solution with saturated CO₂ injection. Solution with different acidity were applied which has pH 4, 5, and 6 respectively. To simulate the flow rate, a Rotating Cylinder Electrode RCE was used at various rotation rates 0, 375, 750, 1500, and 3000 rpm, at room temperature (25°C) and atmospheric pressure. Based on testing results, the changes in rotation converted to flow rate showed that the corrosion mechanism of API 5L X52 steel in NaCl solution with saturated CO₂ content was mainly controlled by mass transport at pH=4 whereas chemically controlled involved both at pH=5 and pH=6 conditions.

Abstract: An analysis is conducted and solutions are provided for the dynamic performance of high speed hybrid thrust bearing. By adopting bulk flow theory, the turbulent Reynolds equation is solved numerically with the different orifice diameter and supply pressure. The results show that increasing supply pressure can significantly improve the bearing stiffness and damping, while the orifice diameters make a different effect on the bearing stiffness and damping.

Abstract: To improve the calculation of the flow properties of an aerospike nozzle, different turbulent models are studied in this research. The primary shape of the nozzle and the plug is determined through utilizing an approximate method. The flow field is then simulated using Navier-Stokes equations for compressible flow. The computational methodology utilizes steady state density-based formulation and a finite volume cell centered scheme to discretize the flow field equations. To accelerate the solution convergence, the flow field is divided into several zones. Each zone is facilitated with proper unstructured grid and appropriate initial conditions are implemented to each zone. The accuracy and the robustness of wall function based turbulence models i.e. standard and RNG k-ε models are compared with those of Spalart-Allmaras (S-A) and k-ω turbulence models.

Abstract: This paper presents results obtained from the application of a computational fluid dynamics (CFD) code Fluent 6.3 to modeling of elevated pressure methane non-premixed sooting flames. The study focuses on comparing the two soot models available in the code for the prediction of the soot level in the flames. A standard k-ε model and Eddy Dissipation model are utilized for the representation of flow field and combustion of the flame being investigated. For performance comparison study, a single step soot model of Khan and Greeves and two-step soot model proposed by Tesner are tested. The results of calculations are compared with experimental data of methane sooting flame taken from literature. The results of the study show that a combination of the standard k-ε turbulence model and eddy dissipation model is capable of producing reasonable predictions of temperature both in axial and radial profiles; although further downstream of the flame over-predicted temperature is evidence. With regard to soot model performance study, it shows that the two-step model clearly performed far better than the single-step model in predicting the soot level in ethylene flame at both axial and radial profiles. With a modification in the constant α of the soot formation equation, the two-step model was capable of producing prediction of soot level closer to experimental data. In contrast, the single-step soot model produced very poor results, leading to a significant under-prediction of soot levels in both flames. Although the Tesner’s soot model is simpler than the current available models, this model is still capable of providing reasonable agreement with experimental data, allowing its application for the purpose of design and operation of an industrial combustion system.

Abstract: According to the basic principle of CFD simulation and methods, a framework structure was studied for its vortex-induced vibration and control principle of around the flow field, it revealed the characteristics of vortex-induced vibration and rules, systematically studied frame structure fluid-solid coupling effect and the flow field active control methods and mechanism. Results provide the theory basis for the frame structure around the flow field and the wind induced vibration effect.

Abstract: Due to T-tube tee is used mostly to connect ducts of the central air conditioning system, different angles of branch pipes caused different local resistance changes. This paper studied two-dimensional turbulent numerical simulation about inter flow of two kinds T-tube by numerical calculation software (CFD),in the method of implicit separation and standard k- ε two equations model, it is clear known that two kinds of forms tee fitting Angle of the internal flow field, Through the contrastive analysis of flow characteristics, it is obvious that local resistance of the oblique angled T-tube tee is much smaller than the common T-tube tee, and also is much more homogeneous.