Computational Fluid Dynamics (CFD) is a branch of fluid mechanics that uses numerical methods and algorithms to simulate the behaviour of fluids — liquids and gases — as they flow through or around structures and equipment. In industrial engineering, CFD allows engineers to visualise and quantify flow patterns, pressure drops, temperature distributions and phase interactions inside real equipment before a single piece of steel is cut.
For oil & gas and petrochemical facilities in Saudi Arabia, where equipment performance directly affects throughput and safety margins, CFD has moved from an academic tool to a routine engineering deliverable on medium and large-scale projects.
How CFD Simulation Works
Like FEA, CFD follows a pre-process / solve / post-process workflow, but the governing equations are different. CFD solves the Navier-Stokes equations — conservation of mass, momentum and energy — across a computational mesh that represents the fluid domain.
Domain Definition and Meshing
The fluid space inside (or around) the equipment is extracted from the CAD geometry and meshed into cells — typically tetrahedral, hexahedral or polyhedral. Near walls where velocity gradients are steepest, a refined boundary layer mesh is used. For most industrial equipment, cell counts range from 500,000 to 20 million depending on complexity and required accuracy.
Boundary Conditions and Turbulence Models
Inlet conditions (velocity, mass flow rate, temperature), outlet conditions (pressure, backflow properties) and wall conditions (no-slip, heat flux, wall temperature) define the problem. For turbulent industrial flows, engineers select an appropriate turbulence closure model — k-epsilon for free-shear and recirculating flows, k-omega SST for flows with adverse pressure gradients and separation, or more advanced approaches for rotating machinery and combustion.
Solving and Convergence
The solver iterates until the residuals — the imbalance in each governing equation — fall below a defined convergence criterion. For steady-state industrial simulations this typically takes hundreds to thousands of iterations. Transient problems (slug flow, sloshing, surge) require time-stepping and are significantly more computationally intensive.
Industrial Applications of CFD Simulation
Heat Exchangers
CFD is used to optimise baffle geometry in shell-and-tube heat exchangers, identify hot spots and maldistribution in the tube bundle, and evaluate the effect of fouling. It can reveal whether a heat exchanger is under-performing due to flow bypassing — a problem invisible in a thermal rating sheet.
Separator Vessels
Three-phase separators rely on gravity and residence time to separate gas, oil and water. CFD simulates inlet momentum (from the inlet distributor), droplet trajectories and the gas-liquid interface to confirm separation efficiency at design and off-design throughputs. Poorly designed internals cause liquid carry-over — a safety and product quality issue.
Silos and Hoppers
Bulk solids handling uses CFD and discrete element method (DEM) coupling to predict flow patterns in silos — whether material will flow in mass flow or core-flow regime, and whether arching or rat-holing is likely. This informs hopper half-angle, outlet size and vibrator positioning before fabrication.
HVAC and Ventilation Systems
For occupied control rooms, electrical substations and enclosed processing areas, CFD models the air distribution from supply diffusers and exhaust grilles to confirm that all zones meet temperature and air change requirements. It is also used for smoke ventilation and emergency gas dispersion studies.
What a CFD Study Delivers
A well-structured CFD report for industrial equipment should provide:
- Velocity vector plots and streamlines showing flow paths and recirculation zones
- Pressure contour maps identifying high-loss regions and pressure drop values
- Temperature distribution plots for thermal simulations
- Phase fraction contours for multi-phase separations
- Quantitative performance metrics: pressure drop, heat duty, separation efficiency, temperature uniformity
- Design recommendations to resolve identified issues
SLETEC's CFD simulation services cover single-phase and multi-phase flow, heat transfer and gas dispersion studies. Our team uses ANSYS Fluent and SolidWorks Flow Simulation to deliver validated results with full report documentation suitable for client submission and operator review.