Yamaha Motor wins MSC Nastran award for co-simulation.

Hexagon’s Manufacturing Intelligence division is focused on using data to help its customers run more efficient operations. Inside this division sits the company’s Design and Engineering Software department, which is dedicated to using computer-aided engineering (CAE) tools to improve products and processes. Since acquiring MSC and Nastran in 2017, Hexagon has continued to develop that software to meet the needs of its customers.

Yamaha’s FAZER R aircraft designers uses co-simulations during development to visualize airflow. (Image courtesy of MSC.)

Recently the Manufacturing Intelligence division announced that Yamaha Motors had won the 2021 MSC Nastran Excellence Award, an award given annually to “recognize our many users around the world who apply FEA to design and manufacture everything from planes, automobiles, ships, electronics, medical devices, to any other product you can imagine.”

The winning application from Yamaha revolved around co-simulations and the simulation of unmanned helicopters. It also outlined many benefits that CAE tools can bring to various engineers within the product design industry.

Yamaha has a long history of manufacturing unmanned helicopters. The company has been building these aircraft for decades, with the Yamaha Operator Support System (YOSS) released in 1990. One of the main goals is to make the copters “easy to operate for as many people as possible.”

Agricultural applications are the target market for the aircraft, but some research institutions also fly the vehicles to perform inspections and provide aerial coverage during disaster relief events. Core competencies for these aircraft include small engine technology, fiber-reinforced polymer (FRP) technology and electronic control technology.

The FAZER R helicopters can carry up to 35 kilograms up to altitudes of 2,800 meters. The overall size of the aircraft is 2,782 millimeters long, 770 millimeters wide, and 1,078 millimeters tall. The main rotor has a 3,115-millimeter diameter and the tail rotor has a 550-millimeter diameter. Yamaha’s rotor design and manufacture use fiber-reinforced polymer as a base material instead of carbon fiber, metal or wood.

A visualization of blade deformation in CoSim. (Image courtesy of MSC.)

Using FRP as the rotor material gives performance that is lightweight but strong. The two rotor blades weigh around 1,700 grams each, and each set of blades are a coordinated pair with the weight difference that is under 5 grams. If an impact occurs, the FRP is less likely to break than other materials, helping to lessen the possibility of operator injury or additional aircraft damage from shattered components. Designing these blades is a study in compromise between torsional stress on the fuselage, controlling the aircraft’s center of gravity, and balancing weight distribution from the agricultural spray tanks. Acoustics only adds to this complicated trade-off analysis. One of the methods that Yamaha uses to maximize the competing constraints of blade design is simulation.

One of the key areas for simulation studies on the FAZER R was noise reduction. Agricultural applications are often close to residential areas, especially in populated areas. One of Yamaha’s concerns was keeping noise levels low around population centers, and a secondary concern was protecting the hearing and fatigue levels of the operators. On a macro scale, noise pollution can have severe negative effects on the health of citizens. High blood pressure, sleep loss, stress-related illnesses and hearing loss are all possible harmful effects of noise pollution. Any commitment to sustainability in manufacturing or drone operation should include some consideration of acoustic levels.

The simulation of components is not necessarily commonplace at this point, but many companies have been doing it for decades. Adding in several components to simulate assemblies adds a degree of difficulty, as engineers must look at each specific interface and then holistically view the whole system. Multidisciplinary studies like the one on the unmanned helicopter crank up the complexity one more notch because these designers were working to understand the thermal, fluid flow and acoustic performance of the aircraft at the same time.

Acoustic and fluid simulation work together to show sound waves. (Image courtesy of MSC.)

On a small project with a few engineers or programmers, a multidisciplinary simulation might be more manageable. When two or three engineers are doing most of the work on a project, they become the subject matter experts and access the component and system data multiple times a day. However, at a large company like Yamaha, it is much more likely that engineers from several divisions or departments will work on a simulation project. Hexagon software can manage data and give several employees access to that data with change control and collaboration tools.

The science of helicopter noise is large and unwieldy, with many different parties holding opinions on the different components creating noise. Rick James from PilotTeacher even breaks down a body’s location relative to the helicopter as an indicator of noise source and intensity. Someone standing close to the aircraft on the ground might hear the engine loudly, but when a helicopter is passing overhead, the rotors are going to produce the loudest noise, creating aerodynamic vortices. Aerocorner.com pins the acoustic level of helicopters at 87 decibels when they are flying at 500 feet, dropping to 78 decibels when the aircraft are flying at 1,000 feet. The website also says that more noise is generated when copters are turning, decelerating and descending because changing direction shifts the pattern of the rotor blades hitting those air vortices.

Ed Brotak from Vertical magazine breaks the noises into three groups—loading and broadband noise, thickness and high-speed impulsive noise, and blade-vortex interaction noise. Loading noises come from the lift and drag forces acting on the blades during operation. Thickness noises are generally horizontal moving waves that are caused by blades moving through air and the resultant air displacement. Blade-vortex noises are sometimes called “blade slap” and create vibrations in the air, aimed in a downward direction.

The engineers at Yamaha had to take all the noise generation concerns into account when dealing with the constraints of the blade design. Controlling the rotor speed and the shape of the blades were the two factors that the team focused on, keeping in mind that small changes in either of these areas could wildly affect the aircraft’s overall performance. Instead of leaving these optimization studies to physical prototypes and late-stage testing, the engineers decided to turn to simulation as an early tool to understand noise generation.

Using the MSC CoSim Engine, the engineers were able to bring together the acoustic, structural and fluid flow concerns and build a complete model of the rotor blades. Data could be moved in and out of the different solvers to see how different analysis methods would react to design changes. MSC Nastran and scFLOW were chosen as the structural and fluid flow tools for the study. The software was used to simulate the airflow resulting from the rotors and their deformation. Actran was the acoustic tool that calculated fluid noise levels from the rotor.

The CoSim Engine is built for MSC Nastran and scFLOW at a source code level, although a different mesh is generated for each software application. Displacement and fluid force data was shared between the two tools because mapping functions kept the data points spatially consistent. Recent improvements to scFLOW’s mesh morphing and deformation visualization also helped to speed up the co-simulations. Actran operators could then take the aero-acoustic profiles from the thermal and computational fluid dynamics (CFD) results to perform a Fourier transform. Sound wave propagation analysis was performed next using the finite element tools in Actran.

Using co-simulation helped Yamaha to find that the blades would rise and fall in small amounts with the airflow, in addition to the factors of pressure distribution and vortex generation. Actran sound simulation gave the engineers a visual model of the soundwave generation’s direction and magnitude. Graphing frequency vs sound pressure level helped them to understand the optimized operating parameters for blade speed.

Access to these findings in the simulation phase of development, instead of waiting for prototypes translates, saved time and money. Yamaha used the data to optimize its helicopter design and performance while making business decisions related to marketing and customer satisfaction. Kenta Mizuno from the Robotics Division of Yamaha said in a white paper, “By increasing the efficiency and speed of the process from design, analysis and prototyping, to the specification determination, we can develop tailor-made main rotors optimized for industry and usage. The visualization of sound, which is invisible, has a great impact on the design development of an unmanned helicopter. As for noise countermeasures, we can consider concrete steps such as planning flight routes and flying guidelines, and can suggest not only manufacturing, but also new

businesses or services.”

Giving out an award to companies that are already using your product creates a mix of marketing materials, case studies for future use and recognition of the hard work of others. MSC has such a wide range of software that it’s nice to see a few of its offerings used on this hyper-specific application. The innovation here that most engineers should appreciate is that a company allows its software tools to operate almost in sync with each other, and the combined data cases can be imported into a third software program to create new analyses. In this case, it saved the Actran engineer a huge share of setup time, by not having to create new boundary conditions or even import the models into the software.

If the goal of simulation is to make better decisions higher up in the development process, then this project shows how that can be a huge success. Yamaha used available tools in a novel way and improved their process. Sometimes the one-time creation of these specific use cases will save a company time in each subsequent quotation because they can use this base data as a platform for each new customer need.

The MSC Nastran Excellence Award is a yearly affair, and the awards page displays not just this case but also a few runners-up and the 2021 Academic Award winner. It’s great to see what designers all over the world are doing with these simulation tools.