Fully Automated CFD Analysis for Full-Scale Ship Hydrodynamics
CFD in Ship Design
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A Seminar On APPLICATION OF COMPUTATIONAL FLUID DYNAMICS (CFD) IN SHIP DESIGN Presented By Mr. Sameer.V.Kadam Guided By Prof. M.P.Ray Department of Mechanical Engineering. K.K.Wagh I.E.E.R
description
The shipbuilding industry has always been challengened to produce efficient designs in extremely short product development cycles. Nearly 80% of the total costs of a ship are set during the first four weeks of the initial design phase. Thus, to be competitive in a global market, a shipyard has to develop sophisticated design tools for product optimization especially in the early design stage. With the progress of computational fluid dynamics (CFD), it is now being used more often as a performance prediction tool for hull design.
Transcript of CFD in Ship Design
A
Seminar On
APPLICATION OF COMPUTATIONAL FLUID
DYNAMICS (CFD) IN SHIP DESIGN
Presented By
Mr. Sameer.V.Kadam
Guided By
Prof. M.P.Ray
Department of Mechanical Engineering.
K.K.Wagh I.E.E.R
WHAT IS CFD?
1. Fluid phenomenon is based on the laws of physics, such as the law of
conservation of mass, Newton’s second law
2. Laws and boundary conditions form P.D.E’s
3. CFD is the art of replacing P.D.E’s with their algebraic form
WHY GO FOR CFD?
EXPERIMENTS SIMULATIONS
Quantitative description of fluid flow
phenomena using measurements.
• for one quantity at a time
• at a limited number of points
and time instants
• for a laboratory-scale model
• for a limited range of problems
and operating conditions
Quantitative prediction of flow
phenomena using CFD software.
• for all desired quantities
• with high resolution in
space and time
• for the actual flow domain
• for virtually any problem and
realistic operating conditions
MAIN STEPS IN CFD SOLUTION
1. GRID GENERATION: Divide the whole body into discrete points
2. DISCRETISATION: Reduce differential equations to algebraic expressions
3. SOLUTION: After solving the equation with help of computer the solution is obtained ABOVE PHOTO SHOWS MESH ON
RIGHT SIDE AND SOLUTION ON LEFT
REQUIREMENT OF CFD IN SHIP DESIGN
1. Ship design deals with a vehicle passing through the two fluids - air and water simultaneously.
2. Moreover the shipbuilding industry has always been challenged to produce complex individual designs in a very short time.
3. Every day's problem of a designer is to find a technical object (hull, propeller, rudder) which satisfies the given boundary conditions in the best way.
AREAS OF INTEREST
1. Critical areas of CFD application in ship design are propeller and hull, out of
which hull has a wider scope for CFD application
2. CFD can be used as a performance prediction tool for hull design.
3. Integrating CFD technique with databases comprising CAD, model tests
and experiments on actual ships, a better hull shape can be found out
METHODS USED
1. Panel Method and Navier Stokes programs are two general classes of CFD programs that apply to the issues of boat design.
2. The most commonly used and most available are Panel Method programs. Panel methods programs are referred to as “inviscid” analysis methods.
3. Viscous drag computations are computed by specialized codes known as Navier Stokes programs.
HOW CFD IS APPLIED IN HULL DESIGN
1: MESH GENERATION
1. Initially an algorithm is developed to implement the laws of momentum and
boundary conditions
2. Architect or a fluids dynamicist is required to generate the key initial input to
a CFD program called a mesh.
3. The detailed shapes of the hull and appendages must be defined by a
mesh of square patches that adjoin one another
HOW CFD IS APPLIED IN HULL DESIGN
1: MESH GENERATION
Use Of CAD Software In Mesh Generation
HOW CFD IS APPLIED IN HULL DESIGN
2: APPLYING OF A SUITABLE METHOD
1. Incase of a panel method it is a good approximation to suppose the wave making to be basically unaffected by viscosity
2. The viscous boundary layer and wake field and the wave breaking and formation of spray are neglected
3. A velocity potential may be defined, such that the velocity field is the gradient of that scalar potential.
4. The incompressibility of the flow requires that the potential satisfy the Laplace equation:
HOW CFD IS APPLIED IN HULL DESIGN
3: BOUNDARY CONDITIONS
1. Boundary condition on the hull surface: On the wetted part of the hull the
normal velocity is zero.
2. Boundary condition to determine the dynamic trim and sinkage.
3. Boundary conditions on the water surface: The kinematical condition states
that the flow must follow the wavy water surface; the dynamic condition
requires that the pressure at the water surface is equal to the atmospheric
pressure
4. Radiation condition: No waves may occur upstream of a disturbance that
generates them
HOW CFD IS APPLIED IN HULL DESIGN
4: EVALUATING BOUNDARY CONDITIONS
1. Cover the boundaries of the flow domain with source panels
2. The total flow field is now defined to be the sum of the velocity fields
induced by all source panels
3. Enforce the boundary conditions on a finite set of points i.e. panel centers
HOW CFD IS APPLIED IN HULL DESIGN
4: EVALUATING BOUNDARY CONDITIONS
4. Express the velocities induced by all panels at the location of all panel centers in terms of unknown source strengths
5. Substitute these expressions in the boundary conditions and discretize
6. Solve the system to compute velocity and pressure
7. This panel method in principle is a relatively standard technique, introduced by Hess and Smith
HOW CFD IS APPLIED IN HULL DESIGN
5: RESULTS
Velocity Field Around A Hull
HOW CFD IS APPLIED IN HULL DESIGN
5: RESULTS
Wind Velocity
HOW CFD IS APPLIED IN HULL DESIGN
5: RESULTS
Pressure Distribution
HOW CFD IS APPLIED IN HULL DESIGN
5: RESULTS
Wave Pattern
HOW CFD IS APPLIED IN HULL DESIGN
5:OPTIMIZATION
