Mirco Valentini - Academia.edu (original) (raw)
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Papers by Mirco Valentini
The paper presents an effective method to evaluate the unsteady flow field around a rotor through... more The paper presents an effective method to evaluate the unsteady flow field around a rotor through a Computational Fluid Dynamics model based on the actuator blade approach. The actuator blade extends the classical actuator disk model without the necessity to perform time or azimuth averaging operations. In this way, a time accurate investigation of the influence of the rotor wake on the rotor itself and on other non-rotating parts (fuselage, wings) can be performed. The method exploits the overset grid technique to allow an easy identification of the location of the sources distributed in the flow field to enforce the correct blade loads. The kinematics and the dynamics of the rotating parts is computed thought the coupling with a multibody solver and transmitted to the CFD as movement of the independent surface grids associated with each actuator blade. This allows to keep into account both rigid and elastic movements, including those related to movable surfaces. A comparison with experimental results obtained for a four blade tiltrotor are shown to verify the quality of the prediction of the flow field. Additionally, a comparison with the results obtained through a classical actuator disk allows to quantify the effects of the employment of the time-accurate approach with respect to the time-averaged results of the actuator disk model.
Traditionally, in numerical weather prediction, the computational cost of performing floating-poi... more Traditionally, in numerical weather prediction, the computational cost of performing floating-point operations (flops) has been the primary concern. However, in the past couple of decades throughput to storage has become a significant bottleneck – a phenomenon often referred to as the input/output (I/O) performance gap. ECMWF runs time-critical operational weather forecasts four times a day, where the entire workflow of each run must complete within one hour. A single run currently produces around 30TiB of data, and it is expected to increase to hundreds of TiB within the next five-to-ten years. This is impossible on existing infrastructure without re-organising how model data is handled and processed. The proposed solution to this problem in the field of weather and climate numerical models has two elements. One is to decouple data output from numerical computations and dedicate pre-defined processes, called I/O-servers, purely to data output. The other is to move computations of ...
A comparison of experimental data with several numerical predictions of the aerodynamic loads on ... more A comparison of experimental data with several numerical predictions of the aerodynamic loads on the ERICA model is presented. The calculations are carried out by several Partners of the NICETRIP consortium, with different codes, turbulence models and grids, with the objective of validating the predictive capability of the CFD tools. Concerning the highly loaded minimum speed aircraft mode AC1, a large separation on the wings has been shown, both by experimental measurements and CFD simulations. Despite this large separation, a good agreement has been obtained between CFD simulations and wind tunnel measurements. Strong aerodynamic interactions between the 4/rev. blades passage and the tiltable wing, the nacelle and the fixed wing loads have been confirmed. Finally, we recommend increasing the aircraft speed flight and reducing the angle of attack for this configuration in order to avoid flow separation and reduce aircraft vibrations. In the highly loaded conversion mode CC4, a good...
Traditionally, in numerical weather prediction, the computational cost of performing floating-poi... more Traditionally, in numerical weather prediction, the computational cost of performing floating-point operations (flops) has been the primary concern. However, in the past couple of decades throughput to storage has become a significant bottleneck – a phenomenon often referred to as the input/output (I/O) performance gap. ECMWF runs time-critical operational weather forecasts four times a day, where the entire workflow of each run must complete within one hour. A single run currently produces around 30TiB of data, and it is expected to increase to hundreds of TiB within the next five-to-ten years. This is impossible on existing infrastructure without re-organising how model data is handled and processed. The proposed solution to this problem in the field of weather and climate numerical models has two elements. One is to decouple data output from numerical computations and dedicate pre-defined processes, called I/O-servers, purely to data output. The other is to move computations of derived (post-processed) data closer to the original “raw” weather data, thus reducing the amount of data to be moved. The challenge then is how to route the combination of raw and post-processed data efficiently to storage without compromising the performance of the running model. We present MultIO, an open-source software library developed at ECMWF for data routing from distributed parallel meteorological and earth-system models. It supports two distinct functionalities. First, it allows the creation of post-processing pipelines to calculate derived meteorological products, such as temporal pointwise statistics, interpolation onto different grids, encoding of data into output formats and output of data storage systems or other consumers. Second, it can act as an I/O-server, creating aggregated horizontal fields from distributed parallel meteorological and earth-system models. MultIO is a key component of the ACROSS project, funded by the EuroHPC JU. It is also partly developed via ECMWF's participation in Destination Earth and is a component of the Digital Twin Engine (DTE).
The paper presents an effective method to evaluate the unsteady flow field around a rotor through... more The paper presents an effective method to evaluate the unsteady flow field around a rotor through a Computational Fluid Dynamics model based on the actuator blade approach. The actuator blade extends the classical actuator disk model without the necessity to perform time or azimuth averaging operations. In this way, a time accurate investigation of the influence of the rotor wake on the rotor itself and on other non-rotating parts (fuselage, wings) can be performed. The method exploits the overset grid technique to allow an easy identification of the location of the sources distributed in the flow field to enforce the correct blade loads. The kinematics and the dynamics of the rotating parts is computed thought the coupling with a multibody solver and transmitted to the CFD as movement of the independent surface grids associated with each actuator blade. This allows to keep into account both rigid and elastic movements, including those related to movable surfaces. A comparison with experimental results obtained for a four blade tiltrotor are shown to verify the quality of the prediction of the flow field. Additionally, a comparison with the results obtained through a classical actuator disk allows to quantify the effects of the employment of the time-accurate approach with respect to the time-averaged results of the actuator disk model.
Traditionally, in numerical weather prediction, the computational cost of performing floating-poi... more Traditionally, in numerical weather prediction, the computational cost of performing floating-point operations (flops) has been the primary concern. However, in the past couple of decades throughput to storage has become a significant bottleneck – a phenomenon often referred to as the input/output (I/O) performance gap. ECMWF runs time-critical operational weather forecasts four times a day, where the entire workflow of each run must complete within one hour. A single run currently produces around 30TiB of data, and it is expected to increase to hundreds of TiB within the next five-to-ten years. This is impossible on existing infrastructure without re-organising how model data is handled and processed. The proposed solution to this problem in the field of weather and climate numerical models has two elements. One is to decouple data output from numerical computations and dedicate pre-defined processes, called I/O-servers, purely to data output. The other is to move computations of ...
A comparison of experimental data with several numerical predictions of the aerodynamic loads on ... more A comparison of experimental data with several numerical predictions of the aerodynamic loads on the ERICA model is presented. The calculations are carried out by several Partners of the NICETRIP consortium, with different codes, turbulence models and grids, with the objective of validating the predictive capability of the CFD tools. Concerning the highly loaded minimum speed aircraft mode AC1, a large separation on the wings has been shown, both by experimental measurements and CFD simulations. Despite this large separation, a good agreement has been obtained between CFD simulations and wind tunnel measurements. Strong aerodynamic interactions between the 4/rev. blades passage and the tiltable wing, the nacelle and the fixed wing loads have been confirmed. Finally, we recommend increasing the aircraft speed flight and reducing the angle of attack for this configuration in order to avoid flow separation and reduce aircraft vibrations. In the highly loaded conversion mode CC4, a good...
Traditionally, in numerical weather prediction, the computational cost of performing floating-poi... more Traditionally, in numerical weather prediction, the computational cost of performing floating-point operations (flops) has been the primary concern. However, in the past couple of decades throughput to storage has become a significant bottleneck – a phenomenon often referred to as the input/output (I/O) performance gap. ECMWF runs time-critical operational weather forecasts four times a day, where the entire workflow of each run must complete within one hour. A single run currently produces around 30TiB of data, and it is expected to increase to hundreds of TiB within the next five-to-ten years. This is impossible on existing infrastructure without re-organising how model data is handled and processed. The proposed solution to this problem in the field of weather and climate numerical models has two elements. One is to decouple data output from numerical computations and dedicate pre-defined processes, called I/O-servers, purely to data output. The other is to move computations of derived (post-processed) data closer to the original “raw” weather data, thus reducing the amount of data to be moved. The challenge then is how to route the combination of raw and post-processed data efficiently to storage without compromising the performance of the running model. We present MultIO, an open-source software library developed at ECMWF for data routing from distributed parallel meteorological and earth-system models. It supports two distinct functionalities. First, it allows the creation of post-processing pipelines to calculate derived meteorological products, such as temporal pointwise statistics, interpolation onto different grids, encoding of data into output formats and output of data storage systems or other consumers. Second, it can act as an I/O-server, creating aggregated horizontal fields from distributed parallel meteorological and earth-system models. MultIO is a key component of the ACROSS project, funded by the EuroHPC JU. It is also partly developed via ECMWF's participation in Destination Earth and is a component of the Digital Twin Engine (DTE).