MSGID: 1:317/3 64af7e1b   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Supercomputer used to simulate winds that cause clear air turbulence   
      
      
     Date:   
         July 12, 2023   
     Source:   
         Nagoya University   
     Summary:   
         Using Japan's most powerful supercomputer, researchers reproduced   
         cases of clear air turbulence around Tokyo. They simulated the fine   
         vortices responsible for this dangerous phenomenon. The usefulness   
         of the simulation in predicting turbulence was confirmed by   
         comparing simulation data with data from aircraft recordings. This   
         research should improve the forecasting of turbulence.   
      
      
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   A research group from Nagoya University has accurately simulated air   
   turbulence occurring on clear days around Tokyo using Japan's fastest   
   supercomputer. They then compared their findings with flight data to   
   create a more accurate predictive model. The research was reported in   
   the journal Geophysical Research Letters.   
      
   Although air turbulence is usually associated with bad weather,   
   an airplane cabin can shake violently even on a sunny and cloudless   
   day. Known as clear air turbulence (CAT), these turbulent air movements   
   can occur in the absence of any visible clouds or other atmospheric   
   disturbances. Although the exact mechanisms that cause CAT are not   
   fully understood, it is believed to be primarily driven by wind shear   
   and atmospheric instability.   
      
   CAT poses a high risk to aviation safety. The sudden turbulence on   
   an otherwise calm day can lead to passenger and crew member injuries,   
   aircraft damage, and disruptions to flight operations. Pilots rely on   
   reports from other aircraft, weather radar, and atmospheric models to   
   anticipate and avoid areas of potential turbulence. However, since CAT   
   shows no visible indicators, such as clouds or storms, it is particularly   
   challenging to detect and forecast.   
      
   As winds swirl and circulate creating sudden changes in airflow,   
   eddies are created that can shake an aircraft. Therefore, to better   
   understand CAT, scientists model it using large-eddy simulation   
   (LES), a computational fluid dynamics technique used to simulate these   
   turbulent flows. However, despite its importance to research on air   
   turbulence, one of the greatest challenges of LES is the computational   
   cost. Simulating the complex interactions involved in LES requires high   
   levels of computing power.   
      
   To elaborately simulate the process of turbulence generation using   
   high- resolution LES, the research group from Nagoya University   
   turned to an exascale computer called the Fugaku supercomputer. It is   
   a high-performance computing system, currently ranked as the world's   
   second fastest supercomputer.   
      
   Using Fugaku's immense computational power, Dr. Ryoichi Yoshimura of   
   Nagoya University in collaboration with Dr. Junshi Ito and others at   
   Tohoku University, performed an ultra-high-resolution simulation of the   
   CAT above Tokyo's Haneda airport in winter caused by low pressure and   
   a nearby mountain range.   
      
   They found that the wind speed disturbance was caused by the collapse of   
   the Kelvin-Helmholtz instability wave, a specific type of instability   
   that occurs the interface between two layers of air with different   
   velocities. As one layer has higher velocity than the other, it creates   
   a wave-like effect as it pulls at the lower velocity layer. As the   
   atmospheric waves grow from the west and collapse in the east, this   
   phenomenon creates several fine vortices, creating turbulence.   
      
   After making their computations, the group needed to confirm whether   
   their simulated vortices were consistent with real-world data. "Around   
   Tokyo, there is a lot of observational data available to validate our   
   results," said Yoshimura. "There are many airplanes flying over the   
   airports, which results in many reports of turbulence and the intensity   
   of shaking. Atmospheric observations by a balloon near Tokyo were also   
   used. The shaking data recorded at that time was used to show that the   
   calculations were valid."  "The results of this research should lead   
   to a deeper understanding of the principle and mechanism of turbulence   
   generation by high-resolution simulation and allow us to investigate the   
   effects of turbulence on airplanes in more detail," said Yoshimura. "Since   
   significant turbulence has been shown to occur in the limited 3D region,   
   routing without flying in the region is possible by adjusting flight   
   levels if the presence of active turbulence is known in advance. LES   
   would provide a smart way of flying by providing more accurate turbulence   
   forecasts and real-time prediction."   
       * RELATED_TOPICS   
             o Matter_&_Energy   
                   # Wind_Energy # Aviation # Aerospace   
             o Earth_&_Climate   
                   # Atmosphere # Weather # Air_Quality   
             o Computers_&_Math   
                   # Computer_Modeling # Distributed_Computing #   
                   Computers_and_Internet   
       * RELATED_TERMS   
             o Supercomputer o Scientific_visualization o Turbulence o   
             Data_mining o Aircraft o Atmospheric_dispersion_modeling o   
             Firestorm o Computer_simulation   
      
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   Journal Reference:   
      1. R. Yoshimura, J. Ito, P. A. Schittenhelm, K. Suzuki, A. Yakeno, S.   
      
         Obayashi. Clear Air Turbulence Resolved by Numerical Weather   
         Prediction Model Validated by Onboard and Virtual Flight   
         Data. Geophysical Research Letters, 2023; 50 (12) DOI:   
         10.1029/2022GL101286   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/07/230712011556.htm   
      
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