DEVELOPMENT AND PERFORMANCE ANALYSIS OF FORCED VORTEX APPARATUS

Vortices are the major component of turbulent flow; the phenomenon is ubiquitous. The quest to study the phenomenon however is being limited by the lack of laboratory equipment to enhance the study. Vortex apparatus enables students and researchers to produce both free and forced vortices and measure the vortex surface profile. Studying natural phenomena such as hurricanes, tornadoes, and whirlpools (free vortices) requires a full understanding of vortex behaviour. The vortex apparatus when manufactured locally will ensure that it is readily available in a most Nigerian university, hence promoting the knowledge and application of vortex and vortex shedding. The apparatus consists of the Hydraulic bench, cylinder vessels, valves, pipes, push-in orifice, impeller, and electric pump. While the material used was water source able from around the environment. 

 

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Table 4.5: Experimental and Analytical Results Showing the Performance of the Forced Vortex Equipment at Minimum - - - - - - - -27

Table 4.6: Experimental and Analytical Results Showing the Performance of the Forced Vortex Equipment at Maximum - - - - - - - -27

 

Fig. 4.3: Experimental and Analytical Results Showing the Performance of the Forced Vortex Equipment at Minimum - - - - - - - 28

Fig. 4.4: Experimental and Analytical Results Showing the Performance of the Forced at Maximum - - -- - - -29 

The study of fluid flow, including vortices and related phenomenon in Nigeria University, is an important area that requires attention, especially amongst engineering departments. Vortices are the major component of turbulent flow; the phenomenon is ubiquitous and has been a subject of interest to engineers as well as to scientists for many years. The quest to study the phenomenon however is been limited by the lack of laboratory equipment to enhance the study. Vortex apparatus enables students and researchers to produce both free and forced vortices and measure the vortex surface profile. A local solution to the design and fabrication of the vortex apparatus is tantamount to the strong development of a strong knowledge base in vortices and related flow phenomenon. 

A flow pattern whereby the streamlines are concentric and fluid the particles do not rotate about their axis while revolving around the vortex centre is known as free or irrotational vortex (Gupta et al, 2014). Vortex dynamics can be traced to the concepts of vortex line, vortex filament and the derivation of vorticity equation for ideal incompressible flow introduced by Hermann Von Helmholtz, Acheson, 1990 (as cited in Gupta et al, 2014). Rankine proposed a classic mathematical model in which vortex motion had an inner core of solid body rotation surrounded by an outer zone of irrational motion.  He derived varieties of equations for the tangential velocity of two regions. A vortex is a special form of fluid motion featured as the rotation of fluid elements and it can be found in many fields of application and nature. 

According to Tian et al(2018), a vortex is a connected region where the vortex vector is not zero. Two types of vortices are distinguished in the dynamics of the motion, forced and free vortices. The forced vortex is caused by external forces on the fluid, such as the impeller of a pump, and the free vortex naturally occurs in the flow and can be observed in a drain or the atmosphere of a tornado.

The wake flow behind a bluff body has been a subject of interest to engineers as well as to scientists for many years. The knowledge and of the concepts and applications of vortex shedding is the key area that should be well studied by university students in Nigeria and beyond. This is because a vortex-shedding phenomenon occurs in nature and can be observed in everyday experiences. A flag waving in the wind, water flowing around bridge piers and pilings, around offshore drilling platforms, around tall buildings etc. Engineers need to take care while designing structures to avoid damage to objects in the path of Vortex Street. 

Studying natural phenomena such as hurricanes, tornadoes, and whirlpools (free vortices) requires a full understanding of vortex behaviour. It is also critical for engineers and designers to be able to characterize forced vortices generated in machineries, such as centrifugal pumps or turbines. Vortices often have adverse effects, as have been seen during hurricanes, tornadoes, or scour holes created downstream of a dam outlet; however, understanding vortex behaviour has enabled engineers to design turbomachinery and hydraulic structures that take advantage of these phenomena.  For example, hydrodynamic separators have been developed, based on vortex behaviour (swirling flow), to separate solid materials from liquids. This type of separator is used in water treatment plants. Students in the university need to be familiar with vortex behaviours and this can be achieved through experimentation with the appropriate apparatus in the laboratory. Vortex apparatus cost is currently quite high in the international market and is further heightened by import duties and currency strength. A local solution to the design and fabrication is desirable to enhance study and experimentation with vortex flow in our universities and laboratories. 

The objective of this study is the development of a vortex apparatus for the study and analysis of vortex flow and dynamics.The specific objectives of this project are:

This project will be designed by finding the appropriate size of the various component of the apparatus that will give the best result. The designed parameters will be used to generate the 3-dimensional model and a draft of the design and drawings will be used to fabricate the drafted apparatus. Finally, the apparatus will be tested and adjusted until satisfactory. Optimization of the manufactured equipment will not be covered in this work. 

The vortex apparatus when manufactured locally will ensure that it is readily available in a most Nigerian university, hence promoting the knowledge and application of vortex and vortex shedding. The various local laboratories and acquired the apparatus for their experimental work. The project after completion will also create jobs locally and add to the country’s domestic product.