Written by Aisling Hughes on August 14, 2019
February 7th, 2018
The life of a product designer or an engineer can be tough. Deadlines, tight budgets, design constraints and quality assurance are what makes this job so challenging—but also so interesting! One of the great things about working at SimScale is getting to see every day how our customers meet these challenges as they design extraordinary products across multiple industry verticals.
Simulations can be a great help when it comes to handling these challenges. It provides early insights into product performance, which allows engineers to make informed design decisions with less prototyping and testing overhead. However, getting the most out of the simulations in a project is sometimes not so straightforward. Therefore, it is wise to keep the following (arguably “corny”) life lessons in mind.
One piece of advice often heard among simulation engineers is “simulate early, simulate often”. This is a philosophy that not only helps simulation engineers keep their job but actually helps to produce a better result in a design project. Early design changes are cheap, so why not try running a few simulations with some rough design concepts to make sure the design project is going in the right direction from the start? The image below shows the creation of a design variant of an early cyclone separator design (done with Onshape).
Simulating these rough concepts is not only significantly easier because fewer details means that less CAD de-featuring is needed, but it also helps you to explore all possibilities and not overlook a good concept.
Before a simulation is run, it’s helpful to ask the question “What would I do differently if I had the simulation results right now?” This helps you concentrate on what is actually important in the simulation you are planning to do. For example, if you are only interested in the numerical value of the pressure drop across a valve, you can leave out a lot of the 3D result processing in the end and directly ensure that the simulation outputs the actual numerical value. In the end, simulation is not an end to itself but a tool to help you build better products, so it’s important that the result data drives your design and is not just beautiful to look at—even though it oftentimes definitely is!
Once you are clear on the type of information you need from the simulation, try to use the easiest and fastest way that gives you “good enough” results first. Running a full-fledged, detailed analysis of your application might make sense later in the project, but in the early stages, it might be more valuable to run fast, iterative, and smaller simulations.
A good example I often see are cooling applications where a solid body (e.g., a casing) is being cooled via an air or a water flow. Before running a full conjugate heat flow analysis that gives you the exact heat transfer coefficient across the solid-fluid interface, why not start with a constant heat transfer coefficient from a book and just simulate the heat transfer within the solid? This kind of simulation is significantly easier and will help you to get the rough concept right (e.g., number of fins, casing material, etc.). Later on, you can pick up “the sledgehammer” for the final detailed analysis as a way to be sure that the design meets the requirements.
In case you really do “need the sledgehammer”—if, for example, you are facing a more complex simulation—, it makes sense to “think big, but start small”. Trying to get the full simulation right in the first step is often difficult to achieve. Start with something simpler, like a coarser mesh or even a simpler geometry that gives you faster turnaround times and makes simulation debugging much more efficient.
The image above shows an initial simulation done for a butterfly valve design project. It has been set up as a steady-state simulation, so just looking at the equilibrium or “final” state of the flow through the valve. This means time-dependent effects, such as transient wakes, are not captured correctly. However, the computing time was just 29 minutes on eight cores, so it’s great for testing if the overall simulation setup, including mesh and geometry, actually works without using a lot of computing time. In the next step, a real transient analysis was set up. It took almost ten times longer to compute but captured all flow effects, as shown in the image below. One can now clearly see the transient flow behavior downstream of the valve.
Translating this phrase to the world of simulation, it would probably be “solving the equations right” ≠ “solving the right equations”. It is not only important that the simulation tool you are using solves the equations well, but also that the user chooses a good strategy to simulate their application. The simulation approach you select can impact the amount of work and time necessary to get the results, as well as their accuracy. To choose a good simulation approach, make sure your application matches the assumptions of the solver you are planning to use (e.g., “No large displacements”, “Mach number below 0.3”, …) and, ideally, don’t start your simulation setup from scratch. Instead, use another successful simulation as a template. With the SimScale Public Projects, we aim to make this a simple choice for you.
Let us know how we can help you to make even more out of simulations for your design projects!
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