Makola M. Abdullah

Prediction of 10-mm Hydrocyclone Separation Efficiency Using Computational Fluid Dynamics

Abstract It has been estimated that particles within the flow field of a 10-mm or mini-hydrocyclone experience local accelerations as high as 10 000 gravitation units. Although their operation is simple, the turbulent, swirling flow field within these devices offers a unique challenge to computational fluid dynamics (CFD). In addition to the computational challenge, very few experimental measurements have been reported in the literature on the flow field of the mini-hydrocyclone to which the CFD results may be compared. This research addresses the issue of predicting the separation efficiency of a volute entry 10-mm hydrocyclone. The feed flow rate is 4.5 litres/m (l/m) yielding a Reynolds number (based on the hydrocyclone diameter) of 9500 and a swirl number of 8.4. Using previously published flow simulation data, a multiphase system (consisting of a discrete oil phase and a continuous water phase) was analyzed for the purpose of obtaining separation information. These separation data were compared with laboratory separation experiments. Results indicate differences less than 20% for each droplet diameter. This information increased the level of confidence in the simulated flow field since there are no published velocity field data for the 10-mm hydrocyclone.

Structural Vibration Reduction Using Fuzzy Control of Magnetorheological Dampers

Control devices can be used in civil structures to dissipate energy from earthquakes, reduce structural damage and prevent failure. Semi-active control devices have been shown to be more energy-efficient than active devices and more effective in reducing seismic structural vibrations than passive devices. A type of semi-active control device, the magnetorheological (MR) damper, consists of a hydraulic cylinder containing micron-sized, magnetically polarizable particles suspended in a liquid such as water, glycol, mineral or synthetic oil. The damping capabilities of this device can be quickly varied by changing the viscosity of the MR fluid from viscous to semi-solid through the introduction of a magnetic field. The objective of this research is to develop a fuzzy controller to regulate the damping properties of the MR damper. Because fuzzy control uses expert knowledge instead of differential equations, it allows for the development of simple algorithms. It does not require accurate information on structural and vibration characteristics of the system and is therefore an attractive alternative for complex and/or nonlinear systems.

Optimal placement of DVFC controllers on buildings subjected to earthquake loading

The dynamic responses of tall civil structures due to earthquakes are very important to the civil engineer. These dynamic responses can produce situations that can range from uncomfortable to unsafe for the building occupants. In recent years classical control theory has been used in civil engineering to reduce the dynamic responses of tall civil structures. Most optimal control algorithms for civil structures involve full state feedback control which requires good estimates of the velocity and displacements throughout the structure. However, there are several important advantages of output feedback control: it takes less computational effort and it has the robustness of passive systems. In this paper, optimal control algorithms are formulated for the optimization of feedback gains and controller placement for building structures. The fundamental basis for these algorithms is the calculation of the gradient of the performance function with respect to the gain matrix. The effectiveness of the algorithm is demonstrated for deterministic earthquake loads in the time domain.

Sensor/actuators placement on civil structures using a real-coded genetic algorithm

The optimal design and placement of controllers at discrete locations on civil engineering structures is an important control problem that will have impact on the earthquake engineering community. Though algorithms exist for the placement of sensor/actuator systems on continuous structures, the placement of controllers on discrete civil structures is a very difficult problem. Because of the nature of civil structures, it is not possible to place sensors and actuators at any location in the structure. This usually creates a nonlinear constrained mixed integer problem that can be very difficult to solve. However, genetic algorithms have been found to be a powerful too in solving such problems. The introduction of algorithms based on genetic search procedures should increase the rate of convergence and thus reduce the computational time for solving the difficult control problem. In this research task, a real coded genetic algorithm will be used to simultaneously place and design a control system for a civil engineering structure. The proposed method of simultaneously placing and designing sensor/actuators will be compared to a similar work that used a hybrid method. The hybrid method involves using a genetic algorithm to place the sensor/actuators, followed by a gradient-based method to determine the optimal controller gains. The proposed method is more convenient, in that both placement and design is done in the same algorithm, and as such it has a better convergence rate than the hybrid method.

Optimal placement of output feedback controllers on slender civil structures at discrete locations

The dynamic responses of tall civil structures due to high winds and earthquakes are very important to the civil engineer. These dynamic responses can produce situations that can range from uncomfortable to unsafe. In recent years classical control theory has been used in civil engineering to reduce the dynamic response of tall civil structures. Many optimal control algorithms for civil structures involve full state feedback control. This method of control requires good estimates of the velocity and displacements throughout the structure. However, there are several important advantages of output feedback control: it takes less computational effort and it has the robustness of passive systems. In this paper, control algorithms are formulated for the selection of feedback gains and controller placement for flexible structures. In some cases, it is necessary to place controllers at discrete locations. For instance, for a tower there might be only several locations that are able to support the equipment needed for a feedback controller. For the placement of controllers at discrete locations in flexible structures, a method is proposed to select gains and placement simultaneously. The effectiveness of this algorithm is demonstrated for stochastic wind loads in the frequency domain.

Placement of feedback controllers on civil structures using genetic algorithms

Genetic algorithms will be used for the optimization of feedback gains and controller placement for discrete building structures. The optimal design and placement of controllers at discrete locations is an important problem that will have impact on the control of civil engineering structures. Though algorithms exist for the placement of sensor/actuator systems on continuous structures, the placement of controllers on discrete civil structures is a very difficult problem. Because of the nature of civil structures, it is not possible to place sensors and actuators at any location in the structure. This usually creates a nonlinear constrained mixed integer problem that can be very difficult to solve. Using genetic algorithms in conjunction with gradient based optimization techniques will allow for the simultaneous placement and design of an effective structural control system. The introduction of genetic-based algorithms should increase the rate of convergence and thus reduce the computational time for solving the difficult control problem.

Placement and Elimination of Vibration Controllers in Buildings

Publisher Summary This chapter reveals the control sensor/actuator elimination method, which has proved to be an effective means of determining the optimal number, placement, and design of sensor/actuators. Dynamic loads on civil structures due to earthquakes can cause excessive vibrations that can lead to serious structural instability resulting in building damage and/or collapse. Building vibrations can be reduced using controller. It is necessary for structural engineers to determine not only the optimal placement and design of these controllers but also the number of controllers required to achieve a predetermined performance. Currently, there are several methods of placing controllers, many of which only consider the placement of a predetermined number of sensor/actuators. In this chapter, a new method is introduced to simultaneously determine the number of necessary controllers, and the optimal placement and design of these controllers needed to retrofit existing structures. To do so, it is assumed that active tendon controllers are placed between every floor of the structure. Controllers are then eliminated in part on their gains and their effect on the buildings response. Controllers with smaller gains are eliminated first, as their effect on the buildings response is insignificant and, therefore, deemed unnecessary. Controllers with larger gains are eliminated according to the buildings response with and without the controller in question. The proposed method is compared to similar work, where a finite number of sensor/actuators are placed sequentially and simultaneously.