Application of CFD

Due to the escalating environmental problems and the anticipated scarcity of fossil fuels, there has been a rapid increase in the demand for renewable energy sources like hydro, solar, and wind over the past few decades. Hydropower, which is primarily produced by hydroelectric dams, is a clean, sustainable energy source that generates less expensive electricity and reduces carbon emissions.

Any hydroelectric power plant’s hydraulic turbine is a key component that influences the plant’s efficiency and, if operated below optimal levels, could result in the loss of useful head. Predicting the behaviour of a hydro-turbine under actual operating conditions is therefore crucial. CFD has become a potent tool for forecasting how mechanical bodies will behave in the presence of dynamic flow conditions. There are numerous examples where analysts at various levels have used this tool to their advantage in order to address a wide range of performance analysis-related issues.

Based on the principles of fluid mechanics, computational fluid dynamics (CFD) modelling employs numerical techniques and algorithms to address issues involving fluid flows. Data structures are used in the science of computational fluid dynamics (CFD) to address problems with fluid flow, such as velocity, density, and chemical compositions.

Nowadays, CFD simulation reports are produced using cutting-edge software platforms like Ansys Fluent, Openfoam, Hypermesh, and Ansys CFX; using CFD software ensures accuracy and speedy completion.

Let’s now explore each and every intricate application in greater detail.

Francis Turbine -:

Francis turbines combine reaction and impulse forces to produce electricity more effectively by having the blades rotate under both impulse and reaction forces of the water flowing through them.

Francis Turbine is an inward-flow reaction turbine. The water enters the turbine radially and exits axially. It has high efficiency as it uses both impulse and reaction forces of the water. It operates under medium heads and medium discharge. It is very efficient and can be used in varied conditions.Widely used in Hydropower plants.

Francis turbine is a reaction turbine which works on the principle of impulse and reaction. Thus, it follows the law of angular instigation. The working fluid converts the part of the available head( implicit energy) into the kinetic energy in the companion vanes and as it moves on the entire blade face which results into energy transfer to the runner blades and the runner shaft from the water so as to produce mechanical energy and further in the form of electricity in alternators. The water is guided by the guide blades to inflow over the moving vanes. Flow of water over the runner is under pressure which traditionally decreases from bay to outlet. Water is admitted each over the circumference of the runner as the runner needs to run full of water since under pressure all the time. The turbine is located between the high pressure water source and the low pressure water exit, generally at the base of the levee. As the water moves through the runner, its spinning compass decreases, further acting on the runner. At the exit, water acts on mug shaped runner features, leaving with no curve and veritably little kinetic or implicit energy. The turbine’s exit tube is shaped to help brake the water inflow and recover the pressure.

The efficiency of Francis Turbine

• In the triangle, the uniform velocities of the inlet and outlet are calculated by u1= (π x D1 x N)/60​ and u2 = (π x D2 x N)/60 where D1 and D2 are the diameter of the outer and inner rings.
• The work done by Francis turbine per unit weight of water can be calculated by = [(vw1​×u1​)±(vw2​×u2​)​]/g
• Discharge of Turbine: The water flow at the inlet or discharge of the turbine can be calculated by Q=π×D1​×B1​×vf1
• The guide vane angle is calculated as, tan⁡∝=Vf1/Vw1 ,where Vf1 and Vw1 are inlet flow velocity and inlet whirl flow velocity.
• The runner vane angle at inlet is calculated as , tan⁡θ=Vf1/(Vw1-u1 ) .
• Runner vane angle at exit is , tan⁡ϕ=Vf1/(Vw1-u1 )
• Ps= wQ/g(Vw1 x u1)
• So now we can calculate the Hydraulic efficiency,
• ηm ​=​Ps​​/wQH where Ps is power developed by runner

Solidworks-:

CFD Analysis -:

1)Pressure-

2) Velocity -:

Result:-

The Design of Francis Turbine is done on Solid works and the Analysis of the turbine is done numerically as well as analytically on CFD Simulation Software “SimScale”.

The results obtained for are,

1. The tangential inlet velocity in terms of Head is 10.28m/s. Inlet Diameter was Calculated which came out to be 0.56m. Outlet Diameter was calculated which came out to 0.28meter.
2. The Inlet and Outlet Velocity came out to be 10.44 m/s and 1.83m/s respectively.
3. Outlet vane angle of the runner is 19.6320.
4. Volume Flow Rate is 0.246m3/s.
5. Width of the wheel at Outlet is 0153m.
6. Hydraulic Efficiency is 97.93%..

SSP Kaimalino:-

Now-a-days CFD methods are widely used in the ship design process, particularly for analysing the flow field as well as for making comparative rankings of hull design variations.For This SHIP-FLOW software is widely accepted software for the purpose of CFD calculations as it has been validated and verified for a wide variety of hydrodynamic applications featuring not only mono hulls but also catamarans and trimarans.

The design process focuses on two problems i.e predicting the speed-power relationship for a complex, twin-strut SWATH (Small Waterplane Area Twin Hull), to determine the main propulsion levels and Calculating the wind field around a semi-submersible platform, to guide the suitable positioning of anemometers for measuring far-field winds

In the late 1960s, SSP Kaimalino was developed by the United States Navy as an experimental vessel.

Unlike traditional ship hulls, the Kaimalino has multiple surface-piercing struts with raked bows; prominent submerged bodies of revolution of varying cross-sectional areas; bulbous bows; multiple lifting surfaces (twin rudders, an aft hydrofoil, and canards at the bow); and twin propeller.
The first application is the prediction of the speed-power relationship for the Stable Semi-Submerged Platform SSP Kaimalino in its current configuration.Potential-flow calculations were first performed using SHIPFLOW and the total resistance was calculated for a number of speeds ranging from 7 to 15 knots. The figure below depicts the perspective view of calculated field flow at 10 knots

Viscous-flow calculations were also performed using SHIPFLOW to calculate the wake fraction and, iteratively, the thrust deduction factor. From these, the hull efficiency at a given speed was obtained. Finally after obtaining the shaft horsepower, the speed-power curve was obtained for the original configuration and current configuration and proposed configuration.

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CFD in electronic Thermal modelling

It’s been a while since thermal analysis is gaining more attention in the field of electronics as it directly affects the performance of the components. CFD softwares are now tailored for the applications in the electronic industry and also the low powerful workstations have made it feasible the simultaneous solutions of both heat transfer and fluid dynamic problems in undertaking thermal design of electronic circuits and systems.A lot of softwares has been developed like FLOTHERM which are specially designed for the use of the electronic industry.

CFD tools now potentially play an important role in the design process of handheld/portable products which compromise a strong portion of today’s electronic manufacturing businesses.Using modelling elements a simulation model is constructed which realistically represent the mockup, while at the same time remaining numerically tractable.

A simulation was carried out on a typical sealed portable/handheld electronic device which completely relies on natural convection for its cooling. The following device was modelled in FLOTHERM as shown in the above figure.

The figure above represents the predicted velocity of air through the device and also the heat dissipation which is shown by the temperature distribution. In a design setting, minimising the temperature rise of the circuit board components will commonly be desired. The results of the above simulations were examined to determine the behaviour of board temperature rise as a function of board-to-case gap. While it was expected that the temperature rise would initially increase with an increasing gap,asing gap, the somewhat surprising result is that temperature difference board-to-case monotonically increases with an increasing gap values even after the onset of convection for horizontal and vertical orientations respectively

HVAC Systems

The primary method by which HVAC systems accomplish their objective, whether it be to provide thermal comfort or other specialised indoor conditions, is ventilation (understood as air moving through an enclosed space). Ventilation equipment capacities and parameters are typically dimensioned using general guidelines and rough hand calculations. This strategy typically results in the specification of oversized equipment, which raises initial costs and energy consumption. In this case, CFD saves the day by providing accurate forecasting of the performance of a ventilation system by simulating physical phenomena, environmental factors, and the intricate geometry of the precinct.

We’ll look at a few typical ventilation system design examples and discuss the advantages of conducting the analysis using CFD.

Passive Ventilation

This technique, also referred to as natural ventilation, uses buoyancy and wind flow to create pressure differences that cause air changes inside the building. Because it has the ability to precisely model unique phenomena like buoyancy caused by temperature or humidity differences, CFD is an extremely effective tool for predicting the behaviour of passive ventilation systems. Additionally, it can account for almost any geometrical feature, allowing for the testing and validation of creative solutions prior to prototyping or construction.

Ventilation Equipment

When a passive ventilation strategy is not enough to comply with performance requirements, a forced ventilation strategy is needed. CFD is extremely helpful when designing air movement equipment. Engineers are now able to forecast performance in terms of pressure distributions, flow directions, and speeds. Then, quickly compare and test different design iterations, all in a virtual setting.

Displacement Ventilation

In the traditional mixing ventilation strategy, conditioned air inlets are placed at the top of the space and at high flow speeds. In contrast, the displacement ventilation strategy places air inlets near floor level and uses relatively low flow speeds. The hot air produced by occupants or equipment rises to ceiling level through buoyancy (the so-called thermal plumes), where it is consolidated and removed from the space without recirculation. A common application of this strategy is found in classrooms and office spaces because it delivers improved air quality.In an office setting, mixing and displacement ventilation strategies are contrasted using CFD simulation.

Thermal Comfort Code Compliance

The evaluation of code compliance is one area where CFD simulation is particularly helpful. Engineers can use CFD to measure parameters at any point in the geometrical space under consideration, including temperature and flow speed. This makes it simple to extract and interpret code performance criteria, allowing for the identification of improvement opportunities.