8 Replies Latest reply on May 23, 2013 7:03 PM by Jared Conway

    Im new, and looking to simulate engine sound from exhaust flow/pulse.

    Kris Kahle

      Hey im Kris. I have an idea and want to get some direction on it.

       

      My idea comes from the horrible quality of engine sound in video games. More specifically racing simulators (like iracing). What i want to do is to find out why a car sounds the way it does. I know there are alot of variables, such as intake pressure, valve timing, exhaust shape, size, ect. but if i have the exact engine specs, and exhaust specs, then if i can sample an engine sound at 500rpm (or just one piston sound) then i, "in theory" should be able to simulate the sound at 20,000 rpm (yes formula 1 engines, 2005 spec).

       

      http://www.youtube.com/watch?v=gT36kC2pwAc

      and

      http://www.youtube.com/watch?v=o_QyUD6V5_I

        • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
          Kris Kahle

          A little info on the engine spec.

           

          Facts and figures:

          • Output of the BMW P83 is over 900 bhp.
          • Maximum engine speed is 19,200 rpm.
          • In a race, engine speed is limited to 19,000 rpm.
          • Idle speed is 4,000 rpm.
          • The engine weighs less than 200 pounds.
          • It covers over 300 miles between refreshening.
          • Total production of the BMW P83 is 200 units, ten of which the team takes to each race.
          • Before being phased out the engine will have received 1,388 upgrades and modifications.
          • It comprises around 5,000 individual components, 1,000 of them distinct.
          • The air consumption is almost 21,500 cubic feet per hour.
          • Maximum piston acceleration is 10,000g.
          • Piston speed peaks at 131 feet per second and on average, reaches 82 feet per second.
          • Exhaust temperatures of up to 1,742 degrees (F) are reached.
          • Maximum air temperature in the pneumatic system is 482 degrees (F).
          • The ultra-high-speed 130R turn at Suzuka with its lateral load of 4g poses the greatest challenge to the oil system.
          • The BMW P83 endured the highest full-throttle proportion on the Monza circuit at 73 percent per lap.
          • At the Monaco Grand Prix, the transmission and engine averaged 3,100 gear changes.
          • The engine block and cylinder head are made of cast aluminum and are manufactured at the BMW Formula One foundry in Landshut using a special thin-wall casting method.
          • BMW Munich handles, among other things, the manufacture of the crankshaft (steel), camshaft (case-hardened steel) and camshaft covers, as well as the machining of the cylinder head and crankcase. The oil system and engine electronics also stem from BMW Munich.

          BMW 83 engine timeline from concept to culmination:

          • Concept: November and December 2001
          • Design: January through May 2002
          • Model construction at the BMW foundry in Landshut: March through May 2002
          • Components manufacture: April through July 2002
          • Initial assembly: July 2002
          • First bench test: July 31, 2002
          • Test phase development stage 1: August 2002 through January 2003
          • First deployment in car: September 18, 2002
          • Development to race readiness: October 2002 to mid-February 2003
          • Further development: mid-February to season's final in October 2003
          • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
            Kris Kahle

            I forgot to even ask my question lol..  With the results of how the pulses flow through the exhaust, and the results from how the gases work after being combusted, i should be able to determine the pitch/tone of where each rpm sample sound should be, and what it should sound like. After that i shoudl be able to edit a sound file of one single combustion sound sample, into an entire rev range, including throttle positioning. Any idea's on how a flow simulation would assist me?

              • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
                Jared Conway

                in the first post you propose this method:

                 

                "I know there are alot of variables, such as intake pressure, valve timing, exhaust shape, size, ect. but if i have the exact engine specs, and exhaust specs, then if i can sample an engine sound at 500rpm (or just one piston sound) then i, "in theory" should be able to simulate the sound at 20,000 rpm (yes formula 1 engines, 2005 spec)."

                 

                in the second you talk about flow simulation.

                 

                so i'm a bit confused.

                 

                could you use flow simulation to figure out what the flow looks like from the engine out the exhaust pipe...sure.

                would it tell you the acoustic properties...not solidworks flow simulation, there are some other codes that could though.

                could you setup an equivalency, IE flow simulation says this and this is how it sounds, so if another flow simulation is twice that, it should sound like this....i think that is a bit of a stretch.

                 

                i'm sure the big auto manufacturers have tools that help them predict what the sound of an engine is going to be before they design the car. but to do that type of simulation takes some serious computing power to take all the physics into account. it seems like you're aware of that, so i'm not sure where you're going with using flow simulation or what you're end goal is.

                  • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
                    Kris Kahle

                    Well my end goal is to accurately simulate the sound of certian engines using mathmetical anynalsis of what makes, say a boss 302 sound different than a toyota 4cyl. I want to find out how and why engines sound so different throughout the rev range. I thought if i could simulate the flow, compression, expansion, and escape of air through the engine cycle, then with the end result find out what the sound SHOULD be. Im thinking its a long shot but if i have a sound sample at say 500 rpm, and i know the flow/pressure through the engine at that speed, then i was hoping to simulate it at 5000rpm and see the change, and ajust the sound sample accordingly. However not through an entire exhaust system, only through racecars with strightpipes. I want it to be so accurate, that it sends chills down your spine it sounds so real.

                      • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
                        Jared Conway

                        flow simulation isn't a good fit here. to simulate suck, squish, bang, blow you need moving mesh and combustion. neither of those are features of flow simulation.

                         

                        also, it sounds like you really need to be looking at something that handles acoustic modeling. also outside the scope of flow simulation.

                         

                        and then in the long run, to get the "sound" to be accurate, you need an accurate engine model, accurate model of the enclosure it is in..etc...etc.

                         

                        seems to me that if you want it to be closer, you need do some high def recordings and then write an algorithm that generates the "Transient" sound based on the game current conditions.

                         

                        also, i don't imagine what you're talking about doing is unique. i'm sure the guys making games right now have spent thousands of dollars to do what you're talking about and either have come to the conclusion that gamers don't need/want it or it costs way too much to do properly. for me i'm the latter, but also have the opportunity to get out on my motorcycle or car on the track and hear it first hand.

                      • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
                        John Sutherland

                        Does SW CFD simulate open ended systems?

                    • Re: Im new, and looking to simulate engine sound from exhaust flow/pulse.
                      Alessandro Tornincasa

                      Hello KRis,

                      Simulia ABAQUS can do acoustic simulation.

                       

                      Alex