Written by Sneha Shetty
Tuesday, December 22, 2020
Surface roughness selection feature in Autonomous Valve CFD app
By
Sneha Shetty
Pune, India – The simulationHub’s Autonomous Valve CFD app is a cloud-based application dedicated to the valve industry. The app helps the valve manufacturers in the flow verification process of the valves by providing Cv, Kv, Cdt values. In this press release, I am going to talk about how the implementation of surface roughness in the simulationHub’s Autonomous Valve CFD app helped the end-users in getting accurate flow performance results. Let’s see how this benefits the users.
However, the Industry faces some challenges in performing CFD simulations like the requirement of HPC machine, CFD expertise and high-cost software license which makes industry difficult in moving towards the future-centric approach of adopting digital technologies. To overcome these industrial challenges, simulationHub has developed 3 different CFD simulation software, emphasizing three attributes of the product i.e. "Accessibility, Affordability and ease-of-use".
What is Surface Roughness?
Commercial pipes come in a variety of materials and surface properties. The internal roughness of a pipe is an important factor when considering the friction losses of a fluid moving through the pipe due to roughness. The surface roughness of a pipe is the finest (shortest wavelength) irregularities of an internal surface of the pipe resulting from a particular production process or material conditions.
(Source : https://powderprocess.net )
How does consideration of surface roughness help the Autonomous Valve CFD users to get accurate flow performance results?
When we test any type of valve, the surface roughness also contributes to the gross pressure drop caused by valve trim obstruction. Observation from the Validation study, experimental testing, simulationHub’s team feedback, and suggestions from our valuable customers, concluded that surface roughness of the pipe and valve component contributes to pressure drop. So to increase the accuracy of the flow performance result we decided to implement a surface roughness feature in the Autonomous Valve CFD application, that considers the valve and pipe surface roughness in the CFD simulation to predict accurate pressure drop.
Pressure drop in valves can be categorized into two types:
1) Pressure drop due to flow obstruction
2) Pressure drop due to friction
Flow obstruction is due to the valve trim which causes flow separation leading to pressure drop. The variables affecting the frictional pressure drop are surface roughness of pipe and valve body, fluid properties, etc. Any change in one variable will lead to a different value of pressure drop.
The following graph shows the effect of surface roughness on the pressure drop for different types of valves. It is observed that friction pressure drop contributes less in the globe valves and more in the case of ball valves and butterfly valves.
Effect of surface roughness on valve performance
As we know that the Cv value is dependent on the pressure drop across the valve. The change in pressure drop due to roughness affects the Cv values significantly. The term "Net" and "Gross" pressure drop is commonly used in the valve and piping industry. These terminologies can be extended to Cv as well. For instance, if the Cv relation contains only the pressure drop across the valve body and excludes the pipe pressure drop it can well be called "Net Cv". The measurements that we get from flow loop measurement are "Gross Cv" which includes the contribution of pressure drop due to pipe friction loss as well, Thus to compare performance results with flow loop testing results it is mandatory to model pipe friction losses and roughness in CFD.
To know more about the Net and Gross Cv visit the link below:
The following table gives typical roughness values in millimeters for commonly used piping materials.
| Surface Material | Absolute Roughness Coefficient - microns (μ) |
|---|---|
| Aluminum, Lead | 1 - 2 |
| Drawn Brass, Drawn Copper | 1.5 |
| PVC, Plastic Pipes | 1.5 |
| Fiberglass | 5 |
| Stainless steel | 15 |
| Steel commercial pipe | 45 - 90 |
| Stretched steel | 15 |
| Weld steel | 45 |
| Galvanized steel | 150 |
| Rusted steel | 150 |
| Riveted steel | 900 - 9000 |
| New cast iron | 250 - 800 |
| Worn cast iron | 800 - 1500 |
| Corroding cast iron | 1,500 - 2,500 |
| Asphalted cast iron | 12 |
| Galvanized iron | 15 |
(Source : https://www.enggcyclopedia.com )
In the Autonomous Valve CFD app, the user can feed the roughness details in the dialogue box that pops up after uploading the valve geometry. In valve specifications, we have added a section to add the valve roughness and pipe roughness where you can specify the roughness value in microns. By default, app shows a 50-micron value in both pipe and valve roughness box
The app uses the entered values to calculate friction pressure drop directly from the CFD.
About Autonomous Valve CFD app
simulationHub’s Autonomous Valve CFD app is a cloud-based CFD app that solves all the complexity of the CFD by itself and helps the valve manufacturers to get the essential flow performance coefficients like Cv, Kv and Cdt along with insightful contour plots and flow line animations. The app also provides detailed CFD simulation reports compiled in pdf format. The simulationHub platform is powered by machine learning and optimization algorithms which makes the software accurate and fast.
Free trial
Autonomous Valve CFD app offers a 15 days free trial period with 20 free simulation credits. Users can simulate 2 valve designs and generate their performance curves and data for free.
Free trial