key drag forces are the skin drag and pressure drag. The skin drag and pressure drag can be accumulated to get the total drag. The drag coefficient is the ratio of the drag force formed in comparison to the product of the dynamic pressure and area. It is a dimensionless quantity. The factors that affect the drag coefficient is the shape of the body, the roughness of the surface, the viscosity of the fluid and compressibility of the object. The viscosity of the fluid introduces the Reynold Number. In Engineering, a key concept to understand is the Reynolds Number. It is the ratio inertial forces (resistance to motion) compared to the viscous forces (fluid 's internal resistance to flow). It is dependent of the velocity, density characteristic length and dynamic viscosity. It is an important factor as it tell you what type of flow you can expect. It gives a quantitative value that tell us the flow is going to be smooth or unsteady, whether it be Laminar Flow or Turbulent Flow. At Low Reynolds number the viscous forces tend to be greater and via versa. The drag coefficient was calculated…
parameters and grid generation. Computational fluid dynamics is based on the concept of Reynolds averaging of the unsteady Navier-Stokes equation commonly known as (RANS) which are considered by Leishman to be the most adaptable method for analyzing nonlinear viscous flows providing that a suitable turbulence model is employed. In VAWT, this nonlinearity is enhanced by the presence of the dynamic stall phenomenon due to the rapid change in the angle of attack of the blades during turbine…
moving in the air for a longer period of time. The smooth surface shows that that air is separated from the ball closer to the initial point of contact and leaves a larger vortex behind the ball compared to its smooth counterpart, creating a greater amount of drag. Reynolds Number Flow can generally be qualified by two different classifications of motion. Flow in a fluid (liquid or gas) can be observed as relatively smooth laminar flow where flow properties, such as pressure and velocity tend to…
Energy Equation, (3) Where u and v are velocity component along the x and y directions of a Cartesian coordinate system respectively, t is the time, p is the pressure, Re (= ρU∞d/μ) is the Reynolds number, Pr (= μCp/k) is the Prandtl number, T is the temperature, d is the diameter of cylinder, k is the thermal conductivity of fluid, Cp is the heat capacity of fluid, ρ is the density of fluid, μ is the dynamic viscosity of fluid and U∞ is the free stream velocity of fluid. Lift and Drag…
particles of a fluid. A fluid that is forced in a tube has the liquid moving faster as it is closer the axis of the tube and slower when farther from it. 3.1.1 Dimensionless Parameters In analysis of convection heat transfer, it is convenient to convert to non-dimensional the governing equations and combine the variables, which makes the group of dimensionless numbers in order to reduce the number of total variables. 3.1.1.1 Prandtl Number The Prandtl number is the ratio of the momentum…
Each dye of flow depends on the velocity of the fluid. Laminar flow could be determined when the filament appeared as a straight line that passed down the whole length of the tube that occurs at low densities. When the filament found to be fluctuating in water, it is considered as transitional flow due to its velocity at intermediate. Furthermore, turbulent flow could be identified when the filament mixed with the surrounding water randomly after passing a little way along the pipe at high…
This mechanism is source in the formation of boundary layers and is highly sensitive to the Reynold’s number. At low Re values, frictional drag influences the nature of attached flows around a bluff body. In contrast, pressure drag is attributed to motion produced by eddies generated in the flow at higher Re values, but is less sensitive to the Reynold’s number. It is important for separated flows and is associated with the formation of the wake following a bluff body. For streamlined bodies,…
ORIFICE PLATE: Definition: An orifice plate is a device that is used for the measurement of flow rate for reducing pressure or for the restricting flow. An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. When a fluid (either liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of the orifice. But as the fluid is forced to converge to pass through the hole, the velocity increases & the fluid pressure decreases. Orifice Plate…
Fluid dynamics and Bernoulli's equation Moving fluids Fluid dynamics is the study of how fluids behave when they're in motion. This can get very complicated, so we'll focus on one simple case, but we should briefly mention the different categories of fluid flow. Fluids can flow steadily, or be turbulent. In steady flow, the fluid passing a given point maintains a steady velocity. For turbulent flow, the speed and or the direction of the flow varies. In steady flow, the motion can be represented…
completely floats, corrosion protection of all the conversion apparatus and lubrification. Finally drilling at a riverbed could have long lasting consequences on the environment, so all of these should be analyzed in advance \cite{khan2009hydrokinetic}. \subsubsection{Hydropower : An Evolving Technology } Apart from some early commercial systems, most technologies in the field of Pico or Hydrokinetic power are still at the proof of concept phase or research and development stage. So there is…