Service overview
Fluid flow, heat transfer, multiphase, aerodynamic and turbulence simulation. This service is part of that division and is scoped individually around what you need to learn, decide or publish.
Computational fluid dynamics solves the equations of fluid motion and heat transfer numerically on a mesh that fills the flow domain. It lets engineers see quantities that are hard to measure, such as velocity fields inside a device, pressure distribution on a surface or the path of a contaminant through a room, and to test design changes quickly. It also invites overconfidence: a vivid animation does not prove that the physics, the mesh or the boundary conditions are right.
Credible CFD is therefore an exercise in making and defending choices. The flow regime determines whether turbulence must be modelled. The geometry decides how much detail is worth meshing. The boundary conditions must come from measurement or system analysis. And the answer must be checked for sensitivity to the mesh and the model before it is believed. This service is organised around those choices, and it documents them so a reviewer can follow the reasoning.
If you plan to publish the outcome, see manuscript & publication support, for example computational & simulation manuscripts or original research article writing.
What is CFD simulation?
Computational fluid dynamics (CFD) simulation uses numerical methods to solve the equations that govern fluid motion and heat transfer (conservation of mass, momentum and energy) over a discretised geometry. It predicts quantities such as velocity, pressure, temperature and species concentration. How far the results can be trusted depends on geometry fidelity, mesh quality, the physical models chosen, boundary conditions and validation against measurements or reference solutions.
What data is required for an engineering simulation?
Typically: the geometry (CAD or dimensioned drawings), material or fluid properties, operating and boundary conditions, the quantities you need as results, and any measurements or published data for validation. Missing items can often be bounded with documented assumptions, but they widen the uncertainty and are stated in the report.
What this service covers
Problems this service can address
- Unclear which flow regime or turbulence model suits the problem
- Results that change with mesh resolution
- No reference data to judge whether the solution is credible
Methods and analytical approaches
- Geometry clean-up and mesh generation with quality metrics
- Steady and transient finite-volume solution set-up
- Turbulence-model selection and wall treatment
- Grid-convergence assessment and validation against reference data
Applications
- Flow around and through components
- Mixing and ventilation studies
- Support for the computational sections of papers
Relevant engineering disciplines
Scope, inputs and deliverables
Scope of work
- Definition of the physics, geometry and quantities of interest
- Model set-up with verification and, where data allow, validation
- Parametric or sensitivity studies agreed at scoping
- Results and documentation suitable for reports or publication
- Feasibility check on: geometry (CAD or drawings) and operating conditions
Typical inputs required from you
- Geometry (CAD or drawings) and operating conditions
- Fluid properties and boundary data
- Any experimental or published reference results
Deliverables
- CFD model description and assumptions
- Velocity, pressure and scalar field results with quantitative comparisons
- Mesh-sensitivity and validation summary
Highly specialised requests are first checked for feasibility from this information. Please do not send confidential data through the public form; describe it first and agree secure transfer afterwards.
Project workflow and method
- 01Enquiry and requirement assessment
- 02Technical scoping and proposal
- 03Execution
- 04Quality review and delivery, with an agreed round of revisions
Read the full project workflow.
In depth: how the work is done
Defining the flow problem and the quantities of interest
We start with the engineering question: pressure drop, heat transfer coefficient, mixing quality, residence time, force on a body or the extent of recirculation. Each demands a different level of resolution and a different validation target. Flow regime is estimated from Reynolds number and, where relevant, Mach, Richardson or Rayleigh numbers. These estimates decide whether the flow is laminar, transitional or turbulent, steady or inherently unsteady, incompressible or compressible, and whether buoyancy, rotation or free surfaces matter. Writing them down before meshing prevents wasted effort.
Geometry preparation and meshing
CAD geometry usually contains features irrelevant to the flow, such as fillets, fasteners and small gaps, and defects that prevent meshing. Clean-up removes or simplifies them while preserving features that govern the flow. Mesh generation balances resolution against cost: finer cells in boundary layers, wakes, shear layers and regions of strong gradients, coarser elsewhere. Quality metrics such as skewness, aspect ratio and smoothness of size changes are checked, and inflation layers are designed for the chosen wall treatment so that near-wall resolution is consistent with the turbulence model.
Physical models, turbulence and boundary conditions
Reynolds-averaged models are efficient and suitable for many engineering flows, but their accuracy varies with the flow type: separation, swirl and strong curvature are classic challenges. Large-eddy and hybrid approaches resolve more of the turbulence at higher cost. Wall treatment, either resolving the viscous sublayer or using wall functions, must match the near-wall mesh. Inlet conditions are specified with realistic velocity and turbulence levels, outlets are placed far enough downstream to avoid influencing the region of interest, and symmetry or periodicity is used only when the flow truly has it.
Solving, converging and checking sensitivity
Steady solutions are judged converged when residuals have dropped appropriately and, more importantly, when monitored quantities such as forces, mass flow balance and temperatures have stabilised. Transient simulations require time steps related to flow time scales and are run long enough to remove start-up effects and gather statistics. Discretisation error is estimated by refining the mesh systematically and comparing results, and the sensitivity to turbulence model and boundary conditions is examined for the quantities of interest. The spread across these tests is a more honest uncertainty than a single run.
Validation and communicating results
Validation compares results with experiments, benchmark cases or well-established correlations. Agreement is quantified for the same quantities and locations, with the uncertainty of the measurement considered. Results are presented as engineering quantities and carefully chosen plots, with scales, units and sampling locations stated. Where no validation data exist, we say so, label results as unvalidated and recommend the measurements that would raise confidence. Reports record software version, models, solver settings and mesh statistics so the simulation can be repeated.
Quality control and good practice
Quality-control approach
- Verification: mesh, time-step and solver sensitivity are examined before results are reported.
- Validation: results are compared with measurements or reference solutions where these exist, and the absence of such data is stated.
- Boundary conditions and material or fluid properties are recorded with their sources.
- Sensitivity to the least certain inputs is shown or explained.
Common pitfalls this service helps avoid
- One mesh, one result. Without refinement or sensitivity tests, the discretisation error is unknown and may exceed the effect being studied.
- Default turbulence model for every problem. A model suited to attached flow may perform poorly for separated or swirling flow.
- Inlet and outlet too close to the region of interest. Boundary placement can distort the flow field and the results of interest.
- Judging convergence by residuals alone. Residuals can stall at levels that look low while monitored quantities are still drifting.
What good reporting looks like
A CFD report states the objective, geometry and simplifications, flow regime estimates, physical and turbulence models with justification, mesh description with quality and refinement results, boundary and initial conditions with sources, solver settings and convergence evidence, results for the quantities of interest with units, validation comparisons and limitations. It distinguishes verified numerical behaviour from validated physical agreement and makes no claim beyond the tested conditions. Input files and settings can be supplied to support reproduction.
An illustrative scenario
Hypothetical example written for explanation. It is not a client case, a result or a testimonial.
Imagine a researcher studying pressure loss in a branched duct. A first simulation with a coarse mesh and default settings gives a plausible total pressure drop. Sensitivity checks show that the result changes noticeably when the mesh is refined near the branch and when a different turbulence model is used. After refinement, the pressure drop settles within a small band, and comparison with measurements from a test rig agrees within the combined uncertainty. The report states the band as the numerical uncertainty and notes that the model has been validated only for the tested flow rates.
Questions to settle before you begin
- Which quantity must the simulation predict, and to what accuracy?
- Is the flow steady, unsteady, laminar or turbulent?
- What measurements or benchmarks can validate the result?
- Are inlet and outlet conditions known from data or assumed?
- How will I test sensitivity to mesh and model?
Key terms
- Reynolds number
- A dimensionless ratio of inertial to viscous forces that indicates the flow regime.
- RANS
- Reynolds-averaged Navier-Stokes modelling of turbulence using time-averaged equations.
- Wall function
- A model bridging the near-wall region so the viscous sublayer need not be resolved.
- Grid convergence
- Behaviour of results as the mesh is refined.
- Boundary layer
- The thin region near a surface where viscous effects are significant.
Working together on Computational Fluid Dynamics (CFD) projects
CFD engagements start with a flow-physics review: expected regime, quantities of interest, available geometry and the measurements that could validate results. A coarse pilot simulation can check set-up and cost before the full study. We ask for geometry in a standard exchange format or dimensioned drawings, fluid properties, boundary conditions and any test data. Reports include mesh and model sensitivity so that you can see how much the answer depends on numerical choices. Results are presented as engineering quantities with units, and limits of validity are stated explicitly.
Frequently asked questions
What do you need to quote a CFD project?
Geometry, fluid and operating conditions, the quantities you need (for example pressure drop or heat flux), and any reference data. See the AEO guide on simulation inputs for a fuller list.
Which CFD software do you use?
The tool is chosen to suit the problem, your existing licences and the need for reproducibility, and is agreed at scoping. Open-source and commercial solvers can both be appropriate.
Can you simulate from a CAD model I send?
Yes, provided the geometry and operating conditions are adequately described. Missing information is listed and assumptions agreed before work starts.
How accurate will the results be?
Accuracy depends on the flow, the models and the quality of input data. Rather than promise a figure, the report quantifies numerical sensitivity and compares with data where available.
Can you support the CFD section of my paper?
Yes. That includes a methods description, validation evidence, figures and responses to reviewer questions on the CFD work.
How is this service scoped and priced?
After your enquiry we review what you need, ask for missing information and send a written scope and quotation. Price depends on complexity, deliverables and timeline. See the project workflow.
Further detail
Who uses CFD services
CFD support is requested by researchers preparing a study, engineering teams without spare analysis capacity, and organisations that want an independent technical view. ENGRexpert is a consultancy: you describe the problem and a suitable specialist or coordinated team is proposed after scoping. It is not a freelancer marketplace and does not state staff numbers or credentials that have not been verified.
Outsourcing a CFD study: what to send
- Geometry or CAD files and the operating conditions
- Fluid properties, boundary conditions and quantities of interest
- Any experimental or reference data for validation
- Target journal or report format, if relevant
Deliverables that can be agreed
- Documented model set-up and assumptions
- Mesh convergence and validation evidence
- Result plots, tables and a written method summary
- Case files where agreed
How a quotation is prepared
Send the requirements through the enquiry form. The scope, assumptions, deliverables, timeline and fee are agreed in writing before work begins. This website states no prices, response times or free-consultation terms. Related services: finite element analysis, engineering optimisation.