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Going with the Flow
Jun30

Going with the Flow

The water industry has a range of engineering challenges and specific regulatory requirements, especially concerning flow assurance, water quality, and even component selection. Learn how CFD delivers real value to the water industry - such as predicting complex flow behavior, across individual components or large network systems.

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Exciting advances in Wind Engineering using ANSYS CFD
Apr14

Exciting advances in Wind Engineering using ANSYS CFD

Wind engineering requires engineers to consider how a building responds to its environment as well as the effect that the structure will have on the space around it. Learn more about the use of CFD in wind engineering...

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Solving Complex Combustion Challenges with CFD
Oct20

Solving Complex Combustion Challenges with CFD

Combustion technology underpins almost every facet of our modern life, from electricity generation to industrial heaters/furnaces through to automotive engines. Increasing social and economic pressure to minimise energy use and reduce pollution is driving the use of CFD to improve the efficiency of combustion processes.

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Turbulence Part 5 - Overview of Scale-Resolving Simulations (SRS)
Sep26

Turbulence Part 5 - Overview of Scale-Resolving Simulations (SRS)

An increasing number of industrial CFD users are recognising the need to move away from RANS modelling and resolve a greater spectrum of turbulence (particularly in cases involving large-scale separation, strongly swirling flows, acoustics, etc.). Here we present an overview of Scale Resolving Simulation techniques and important considerations when considering applying SRS to your project.

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How does the Reynolds Number affect my CFD model?
Mar20

How does the Reynolds Number affect my CFD model?

The Reynolds number (Re) is the single most important non-dimensional number in fluid dynamics and is recommended to be calculated before you begin any new CFD modelling project.  The Reynolds Number is defined as the dimensionless ratio of the inertial forces to viscous forces and quantifies their relevance for the prescribed flow condition: Where U∞ and L are the characteristic velocity and length scale of the problem, ρ  is the fluid density and μ is the dynamic viscosity. The use of the Reynolds number frequently arises when performing a dimensional analysis and is known as Reynolds principle of similarity. For example, air flow of U∞ = 1 [m/s] over a flat plate of L = 1 [m] will exhibit the same flow pattern as air flow of U∞ = 10 [m/s] over a flat plate of L = 0.1 [m]. This concept holds since the Re is equal and the flow is incompressible (i.e. the Mach number is low). The Re also allows us to characterize whether a flow is laminar or turbulent. Laminar flow is characterized by lower Re and high diffusion over convection. Turbulent flow on the other hand is characterized by higher Re where inertial forces dominate considerably, resulting in largely chaotic flow. The flow may also undergo a transitioning phase whereby the flow exhibits neither completely laminar nor completely turbulent characteristics.           Note: Inertial forces are proportional to the square of velocity, while viscous forces vary linearly with velocity. Therefore as the Re → 0 it is reasonable to neglect convective terms (e.g. creeping flow). Similarly, as the Re → ∞ the viscous terms of the momentum equation can be neglected and the problem can be characterized purely by the generation of inertial forces (e.g. high supersonic and hypersonic flows). For flows in a pipe of diameter L or non-circular pipes with hydraulic diameter L, empirical studies have shown that laminar flow occurs for ReL < 2500 and fully developed turbulent flow occurs for ReD > 4000. In the interval between, transition occurs. For external flows (e.g. flow over a flat plate), laminar flow is observed up to approximately ReD ~ 1×105 to 5×105 (where D is the distance from the leading edge) before transition to turbulence takes place and turbulent flow is observed thereafter.               Factors influencing transition include roughness and local acceleration. The Turbulence Modelling team at ANSYS Inc, led by Dr. Florian Menter, have developed world-leading capabilities to allow CFD users to accurately model these transition effects. Using the Reynolds number, we can determine whether or not it is necessary to include...

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