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In the present study CFD simulation with delayed detached eddy simulation (DDES) are performed to investigate pressure fluctuation environment on an open cavity and weapon bay of UAV. The main purpose of this study is to explore the aerodynamic noise level of complex cavities with slant ceiling and irregular length–depth ratio. First, two cases on an open cavity at Ma 0.85 are analyzed to determine the slant ceiling influence, which shows that the sound pressure levels increase by 1 dB due to the transverse flow effect. Then, a typical weapon bay on unmanned aerial vehicle is simulated to investigate the aerodynamic noise environment. The overall sound pressure level in the weapon bay is up to 157 dB, and when the Mach number turns from 0.6 to 0.8, the amplitude of all modes increases about 16–23 dB. The main focuses of this investigation are to discuss the mechanism of noise generation in a slant ceiling cavity and determine the pressure fluctuation characteristic of a typical weapon bay on unmanned aerial vehicle. [ABSTRACT FROM AUTHOR]

In this paper,a simplifiedtransonic weapon baywith a L/D=5 and Mach number 0.85 was considered using the large-eddy simulation(LES)with dynamic kinetic energy subgrid-scale (SGS)model. The M219 geometry has been analyzed using OpenFOAM for three different configurations based on the position of the covers. The obtained results have been validated against reference studies and presented in terms of mean streamwise velocity profile, overall sound pressure level, sound pressure level and band-integrated sound pressure level in both spatial and frequency domains. In order to mitigate the high computational cost associated with acoustic analysis, a Cartesian mesh topology has been employed as an alternative approach. The numerical findings have demonstrated a comparable level of accuracy to simulations conducted with high-cell count meshes. Based on these findings, a cavity analysis has been conducted for the configuration with covers positioned at a position of 45°.

Bu çalışmada Mach sayısı 0.85 ve Reynolds sayısı 1.3x107 için zamana bağlı 3 boyutlu kavite akışı ve kavite boyunca anlık basınç salınımlarından kaynaklı oluşan gürültü açık kaynaklı Hesaplamalı Akışkanlar Dinamiği çözücüsü olan OpenFOAM kullanılarak incelenmiştir. Akış alanı modellemesinin gürültü oluşumuna etkisini gözlemlemek için iki farklı akış alanı modellemesi yapılmıştır. Akış alanı modelinin etkisine ek olarak duvar bölgesindeki ağ sıklığı ve ağdaki hücrelerin büyüme oranlarının aeroakustik bulgular üzerindeki etkisi incelenmiştir. Üç boyutlu akış alanının zamana bağlı incelemelerinde, Büyük Burgaç Benzetimi (LES) ve Ayrık Burgaç Benzetimi (DES) olmak üzere iki türbülans modeli kullanılmıştır. LES analizlerinde küçük girdap yapılarını çözmek için Smagorinsky ve WALE olmak üzere iki ağ-altı ölçek modeli kullanılmıştır. DES analizlerinde Spalart-Allmaras tabanlı DDES, IDDES ve SST k-ω tabanlı DES olmak üzere üç model kullanılmıştır. Transonik kavite için hesaplanan sayısal sonuçlar deneysel ve nümerik sonuçlarla hem konum hem frekans uzayında akustik sinyal verisi için karşılaştırılarak doğrulanmıştır. Analizler sonucu elde edilen konum uzayındaki Ortalama Ses Basınç Düzeyi verisi kavite gürültüsüne ait deneysel veri ile benzer davranışı gösterse de 8-10 desibellik bir sapma görülmüştür. Frekans uzayındaki Ses Basınç Düzeyi sonuçlarında ise Rossiter modları belirgin şekilde gözükmektedir ve hem deneysel hem nümerik çalışmaya yakın sonuçlar elde edilmiştir.

In this paper, a simplified transonic weapon bay with a L/D=5 and Mach number 0.85 was considered using the large-eddy simulation (LES) with dynamic kinetic energy subgrid-scale (SGS) model. The M219 geometry has been analyzed using OpenFOAM for three different configurations based on the position of the covers. The obtained results have been validated against reference studies and presented in terms of mean streamwise velocity profile, overall sound pressure level, sound pressure level and band-integrated sound pressure level in both spatial and frequency domains. In order to mitigate the high computational cost associated with acoustic analysis, a Cartesian mesh topology has been employed as an alternative approach. The numerical findings have demonstrated a comparable level of accuracy to simulations conducted with high-cell count meshes. Based on these findings, a cavity analysis has been conducted for the configuration with covers positioned at a position of 45°. [ABSTRACT FROM AUTHOR]

Summary: Cavity flow research has been ongoing experimentally since the 1940s, especially for weapon bay use in fighter aircraft. Technology advancement has led to the beginning of simulations of experimental studies. The success of these simulations has increased with the emergence of High‐Performance Clusters, and simulation studies have started to take the role of experimental studies. In this paper, an open rectangular, unsteady transonic cavity with a length to depth ratio of 5, Mach number 0.85 and Reynolds number of approximately 6.5 × 106 is simulated using Computational Fluid Dynamics (CFD) on a High‐Performance Cluster. Likewise, cavity door is used to model a real weapon bay. Detached‐Eddy Simulation is used to resolve turbulent properties in the flow domain. Results compatible with experimental data are obtained with OpenFOAM, an open‐source CFD code based on the finite volume method. Additionally, computational costs are given in the clock‐time analysis section, and the necessity of high‐performance clusters for CFD and Computational Aeroacoustics studies is emphasized. [ABSTRACT FROM AUTHOR]

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The internal weapon bay is widely used in modern aircraft; however, because the unsteady flows of the cavity would cause dangerous store separation and intense aerodynamic noise, the leading-edge spoiler is an easy and efficient passive flow-control method. The flow control of the leading-edge flat spoiler before the cavity of a low-aspect-ratio flying-wing aircraft is investigated based on numerical simulation. Numerical results show that the leading-edge flat spoiler completely changes the cavity flow; it obviously lifts up the shear layer and reduces the pressure inside the cavity. For the store separation from the weapon bay, the leading-edge flat spoiler is a very good passive flow-control method that curbs the nose-up trend of the store and produces a safe and stable store separation. Besides, the leading-edge spoiler reduces the noise in the rear of the cavity (max 8.2 dB), but increases the noise in the middle of the cavity (max 11.3 dB). In addition, the leading-edge spoiler brings in a large drag increase to the aircraft (39.41% when the height of spoiler is 0.2 m), which would affect the operational stability of the aircraft. The results of this paper could provide a reference for the flow control of weapon bays and the design of aircraft. [ABSTRACT FROM AUTHOR]

The internal weapon bay is widely used in modern aircraft; however, because the unsteady flows of the cavity would cause dangerous store separation and intense aerodynamic noise, the leading-edge spoiler is an easy and efficient passive flow-control method. The flow control of the leading-edge flat spoiler before the cavity of a low-aspect-ratio flying-wing aircraft is investigated based on numerical simulation. Numerical results show that the leading-edge flat spoiler completely changes the cavity flow; it obviously lifts up the shear layer and reduces the pressure inside the cavity. For the store separation from the weapon bay, the leading-edge flat spoiler is a very good passive flow-control method that curbs the nose-up trend of the store and produces a safe and stable store separation. Besides, the leading-edge spoiler reduces the noise in the rear of the cavity (max 8.2 dB), but increases the noise in the middle of the cavity (max 11.3 dB). In addition, the leading-edge spoiler brings in a large drag increase to the aircraft (39.41% when the height of spoiler is 0.2 m), which would affect the operational stability of the aircraft. The results of this paper could provide a reference for the flow control of weapon bays and the design of aircraft.

An experimental investigation is conducted in a high speed wind tunnel to suppress acoustic resonance. Conventional leading edge mass blowing actuator are used to disturb cavity flow. Detailed static-pressure and fluctuating-pressure measurements are obtained on the cavity walls to determine the effects on cavity flow characteristics. Wind tunnel test based analysis of the suppression of dynamic loads on the walls of a complex weapon bay using leading edge mass blowing is presented. The unique aspect of the concepts discussed here is the very low mass flow rates used to achieve significant suppression. The simulation results are used to gain insight into the mechanism governing the effectiveness of these jets. The PRTB are applied to a deep (L/D = 4. 5) cavity at transonic conditions of Mach 0. 8. The experimental results show excellent agreement with experiments showing an overall reduction of the noise levels of the order of 5 dBs with the control concepts. The primary mechanism of reduction is the break-up of the spanwise coherence in the shear layer into smaller vortical structures thus reducing the shear layer flapping and leading to a smaller imprint on the wall pressures. [ABSTRACT FROM AUTHOR]

The method based on overset unstructured grid technique is developed for the simulation of cavity flows and store separation. The numerical simulation for typical cavity flows and separation trajectory of WPFS model have achieved good agreement with experimental data and shown a promising capability for applications. The numerical simulation of door operation and store separation trajectory has been made to investigate the unsteady effects on aerodynamic characteristics of the door flap. It is found that under certain conditions, the door's movement has a strong effect on aerodynamic characteristics of the door flap, which must be seriously considered during the door flap and control system design procedure. Under current conditions, all the store separation procedure is safe. The present research provides a technical support for door flap design and store separation evaluation. [ABSTRACT FROM AUTHOR]