含運(yùn)動(dòng)邊界鈍體繞流風(fēng)場(chǎng)的大渦模擬數(shù)值算法
發(fā)布時(shí)間：2018-09-17 06:39
【摘要】：薄膜屋蓋結(jié)構(gòu)與風(fēng)場(chǎng)之間的流固耦合作用是影響結(jié)構(gòu)風(fēng)振響應(yīng)的重要因素。數(shù)值模擬是流固耦合研究的重要手段,準(zhǔn)確模擬流體域的時(shí)變特性是掌握流固耦合效應(yīng)產(chǎn)生機(jī)理和發(fā)展規(guī)律的前提。風(fēng)與薄膜結(jié)構(gòu)流固耦合運(yùn)動(dòng)中的流體域是含動(dòng)邊界的鈍體繞流近地風(fēng)場(chǎng),在采用計(jì)算流體動(dòng)力學(xué)(Computational Fluid Dynamics,CFD)技術(shù)對(duì)其進(jìn)行大渦模擬(Large-eddy Simulation, LES)數(shù)值近似計(jì)算時(shí),仍存在一些亟待解決的問(wèn)題。 建立適于大型工程應(yīng)用的亞格子模型是大渦模擬方法理論研究中的熱點(diǎn)問(wèn)題之一。在求解近地風(fēng)場(chǎng)大渦模擬控制方程時(shí),投影法是一種高效的壓力速度解耦算法。目前大多數(shù)投影格式對(duì)壓力的計(jì)算在時(shí)間方向上比速度的計(jì)算至少低一階精度,而壓力場(chǎng)的時(shí)間精度將直接影響流固耦合效應(yīng)的計(jì)算精度。因此,投影法的壓力時(shí)問(wèn)精度還有待提高。此外,動(dòng)邊界繞流模擬適宜在任意拉格朗日歐拉(Arbitrary Lagrangian Eulerian, ALE)動(dòng)態(tài)網(wǎng)格框架下進(jìn)行。模擬過(guò)程中網(wǎng)格更新頻繁,其幾何品質(zhì)和更新前后的一致性是影響模擬精度的重要因素。目前大部分動(dòng)網(wǎng)格更新算法僅關(guān)注更新后網(wǎng)格的幾何品質(zhì),對(duì)更新前后網(wǎng)格一致性的測(cè)試不夠；而動(dòng)網(wǎng)格更新算法的計(jì)算耗時(shí)也是需要考慮的一個(gè)課題。 針對(duì)上述問(wèn)題,本文對(duì)亞格子模型、投影法及其在ALE動(dòng)態(tài)網(wǎng)格下的應(yīng)用以及動(dòng)網(wǎng)格更新技術(shù)等內(nèi)容進(jìn)行了理論和數(shù)值研究,開展的研究工作和提出的解決方案主要包括： 1、亞格子模型的測(cè)試和對(duì)比。在闡述近地風(fēng)場(chǎng)的大渦模擬無(wú)量綱控制方程以及多種亞格子模型的構(gòu)造過(guò)程后,在笛卡爾靜態(tài)網(wǎng)格下編制了方程求解程序。以該程序?yàn)橛?jì)算平臺(tái),對(duì)多種亞格子模型的適用性、準(zhǔn)確性和計(jì)算效率進(jìn)行了測(cè)試。結(jié)果表明,鈍體繞流風(fēng)場(chǎng)的大渦模擬工程應(yīng)用中可以采用阻尼修正的標(biāo)準(zhǔn)S模型。 2、動(dòng)態(tài)網(wǎng)格下數(shù)值求解方法的建立。以ALE描述為基礎(chǔ),在動(dòng)態(tài)網(wǎng)格下建立了大渦模擬控制方程(下文簡(jiǎn)稱ALE-LES方程),并對(duì)方程中的網(wǎng)格運(yùn)動(dòng)參數(shù)和流動(dòng)參數(shù)進(jìn)行解耦,建立了交錯(cuò)求解方程的數(shù)值計(jì)算方法。期間,為提高數(shù)值方法的時(shí)間計(jì)算精度,構(gòu)造了壓力和速度能達(dá)到同一高階時(shí)間精度的全精度連續(xù)投影方法,并將其與求解網(wǎng)格運(yùn)動(dòng)的二階預(yù)測(cè)校正格式相結(jié)合,得到了ALE-LES方程的全二階精度投影格式。將建立的數(shù)值求解方法進(jìn)行坐標(biāo)轉(zhuǎn)換,在貼體坐標(biāo)系下編制了ALE-LES方程求解程序的核心模塊。 3、動(dòng)網(wǎng)格更新算法的對(duì)比研究。歸納整理出網(wǎng)格質(zhì)量評(píng)價(jià)模型,并據(jù)此在兩種畸變網(wǎng)格算例中,為適用于結(jié)構(gòu)網(wǎng)格的多種動(dòng)網(wǎng)格更新算法對(duì)網(wǎng)格幾何品質(zhì)的改善力度進(jìn)行了對(duì)比；同時(shí),對(duì)不同算法在更新前后網(wǎng)格的一致性和計(jì)算效率方面進(jìn)行了測(cè)試,指出九點(diǎn)網(wǎng)格重構(gòu)法綜合性能最為優(yōu)異。將九點(diǎn)網(wǎng)格重構(gòu)法擴(kuò)展到三維研究領(lǐng)域并更名為距離加權(quán)法,據(jù)此編制了網(wǎng)格動(dòng)態(tài)更新子程序模塊。 4、數(shù)值模擬程序的開發(fā)和驗(yàn)證。將亞格子模型子程序模塊和網(wǎng)格動(dòng)態(tài)更新子程序模塊與求解ALE-LES方程的核心程序相結(jié)合,開發(fā)了適用于模擬含運(yùn)動(dòng)邊界鈍體繞流風(fēng)場(chǎng)的CFD計(jì)算程序。分別以二維方腔驅(qū)動(dòng)流和Taylor渦列問(wèn)題驗(yàn)證了程序的穩(wěn)定性和時(shí)間計(jì)算精度。 5、振動(dòng)屋蓋繞流特性的數(shù)值分析。以下部封閉式大跨度平屋蓋結(jié)構(gòu)為研究對(duì)象,應(yīng)用本文開發(fā)程序,對(duì)屋蓋以二階諧波模態(tài)振動(dòng)時(shí)的結(jié)構(gòu)繞流場(chǎng)進(jìn)行了數(shù)值模擬,通過(guò)與相同尺寸剛性屋蓋結(jié)構(gòu)繞流模擬結(jié)果的對(duì)比分析,研究了屋蓋的振動(dòng)對(duì)模型表面風(fēng)壓系數(shù)分布和繞流場(chǎng)流動(dòng)結(jié)構(gòu)的影響。結(jié)果表明,屋蓋振動(dòng)是影響建筑結(jié)構(gòu)表面平均、脈動(dòng)風(fēng)壓系數(shù)的重要因素；屋蓋振動(dòng)導(dǎo)致繞流場(chǎng)旋渦結(jié)構(gòu)復(fù)雜化,特征湍流度增加；屋蓋的振動(dòng)對(duì)繞流場(chǎng)瞬時(shí)風(fēng)壓分布的影響明顯,二階諧波模態(tài)的振動(dòng)形式容易引發(fā)脈動(dòng)風(fēng)與屋蓋的共振,不利于屋蓋的抗風(fēng)穩(wěn)定。自主開發(fā)程序的成功應(yīng)用表明了該程序可作為薄膜結(jié)構(gòu)流固耦合效應(yīng)數(shù)值模擬計(jì)算平臺(tái)的流體域求解器。
[Abstract]:Fluid-structure interaction between membrane roof structure and wind field is an important factor affecting the wind-induced vibration response of structures.Numerical simulation is an important means of fluid-structure coupling research.Accurate simulation of time-varying characteristics of fluid domain is the premise to grasp the generation mechanism and development law of fluid-structure coupling effect. Computational Fluid Dynamics (CFD) technique is used to approximate the large eddy simulation (LES) of a blunt body with moving boundary.
Establishing a sublattice model suitable for large-scale engineering applications is one of the hot issues in the theoretical study of large eddy simulation. Projection method is an efficient pressure-velocity decoupling algorithm for solving the large eddy simulation control equations in the near-Earth wind field. In addition, the simulation of flow around moving boundary is suitable for arbitrary Lagrangian Eulerian (ALE) dynamic grids. In the simulation process, the grid update frequency is used. At present, most of the dynamic mesh updating algorithms only focus on the geometric quality of the updated mesh, and the test of the consistency before and after updating is insufficient. The computational time-consuming of the dynamic mesh updating algorithm is also a problem to be considered.
In view of the above problems, the subgrid model, projection method and its application in ALE dynamic mesh and dynamic mesh updating technology are studied theoretically and numerically in this paper.
1. Sublattice model test and comparison. After explaining the large eddy simulation dimensionless governing equations of the near-Earth wind field and the construction process of several sublattice models, the equation solving program is compiled under the Cartesian static grid. The results show that the standard S model with damping modification can be used in large eddy simulation of wind field around bluff body.
2. Establishment of numerical solution method in dynamic grid. Based on ALE description, large eddy simulation control equation (hereinafter referred to as ALE-LES equation) is established in dynamic grid, and the grid motion parameters and flow parameters in the equation are decoupled. A numerical method for solving the equation is established. During this period, the timescale of the numerical method is improved. A full-precision continuous projection method with the same high-order time precision for pressure and velocity is constructed, and the second-order accurate projection scheme for ALE-LES equation is obtained by combining it with the second-order predictive correction scheme for grid motion. The numerical solution method is transformed into coordinates and AL is programmed in body-fitted coordinates. The core module of E-LES equation solver.
3. Comparisons of dynamic mesh updating algorithms. The mesh quality evaluation models are summarized and sorted out. Based on these two distorted mesh examples, the improvement of the mesh geometry quality is compared for various dynamic mesh updating algorithms suitable for structured meshes. At the same time, the consistency and computational efficiency of different algorithms before and after updating are compared. The nine-point mesh reconstruction method is extended to the three-dimensional research field and renamed as the distance-weighted method. Based on this, a dynamic mesh update subroutine module is developed.
4. Development and verification of numerical simulation program. Combining sublattice model subroutine module and grid dynamic updating subroutine module with the core program for solving ALE-LES equation, a CFD program for simulating the wind field around a bluff body with moving boundary is developed. The program is verified by two-dimensional square cavity driving flow and Taylor vortex train problem respectively. The stability and the accuracy of time calculation.
5. Numerical analysis of the flow around a vibrating roof. The following closed large-span flat roof structure is studied. The numerical simulation of the flow around the roof under the second harmonic mode vibration is carried out by using the program developed in this paper. The vibration of the roof is studied by comparing with the results of the flow around a rigid roof structure of the same size. The results show that the roof vibration is an important factor affecting the average and fluctuating wind pressure coefficients on the surface of the structure; the vibration of the roof results in the complexity of the vortex structure around the flow field and the increase of the characteristic turbulence; the vibration of the roof has an obvious effect on the instantaneous wind pressure distribution around the flow field. The second-order harmonic modes are liable to cause the resonance between the fluctuating wind and the roof, which is not conducive to the wind stability of the roof.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU312.1
[Abstract]:Fluid-structure interaction between membrane roof structure and wind field is an important factor affecting the wind-induced vibration response of structures.Numerical simulation is an important means of fluid-structure coupling research.Accurate simulation of time-varying characteristics of fluid domain is the premise to grasp the generation mechanism and development law of fluid-structure coupling effect. Computational Fluid Dynamics (CFD) technique is used to approximate the large eddy simulation (LES) of a blunt body with moving boundary.
Establishing a sublattice model suitable for large-scale engineering applications is one of the hot issues in the theoretical study of large eddy simulation. Projection method is an efficient pressure-velocity decoupling algorithm for solving the large eddy simulation control equations in the near-Earth wind field. In addition, the simulation of flow around moving boundary is suitable for arbitrary Lagrangian Eulerian (ALE) dynamic grids. In the simulation process, the grid update frequency is used. At present, most of the dynamic mesh updating algorithms only focus on the geometric quality of the updated mesh, and the test of the consistency before and after updating is insufficient. The computational time-consuming of the dynamic mesh updating algorithm is also a problem to be considered.
In view of the above problems, the subgrid model, projection method and its application in ALE dynamic mesh and dynamic mesh updating technology are studied theoretically and numerically in this paper.
1. Sublattice model test and comparison. After explaining the large eddy simulation dimensionless governing equations of the near-Earth wind field and the construction process of several sublattice models, the equation solving program is compiled under the Cartesian static grid. The results show that the standard S model with damping modification can be used in large eddy simulation of wind field around bluff body.
2. Establishment of numerical solution method in dynamic grid. Based on ALE description, large eddy simulation control equation (hereinafter referred to as ALE-LES equation) is established in dynamic grid, and the grid motion parameters and flow parameters in the equation are decoupled. A numerical method for solving the equation is established. During this period, the timescale of the numerical method is improved. A full-precision continuous projection method with the same high-order time precision for pressure and velocity is constructed, and the second-order accurate projection scheme for ALE-LES equation is obtained by combining it with the second-order predictive correction scheme for grid motion. The numerical solution method is transformed into coordinates and AL is programmed in body-fitted coordinates. The core module of E-LES equation solver.
3. Comparisons of dynamic mesh updating algorithms. The mesh quality evaluation models are summarized and sorted out. Based on these two distorted mesh examples, the improvement of the mesh geometry quality is compared for various dynamic mesh updating algorithms suitable for structured meshes. At the same time, the consistency and computational efficiency of different algorithms before and after updating are compared. The nine-point mesh reconstruction method is extended to the three-dimensional research field and renamed as the distance-weighted method. Based on this, a dynamic mesh update subroutine module is developed.
4. Development and verification of numerical simulation program. Combining sublattice model subroutine module and grid dynamic updating subroutine module with the core program for solving ALE-LES equation, a CFD program for simulating the wind field around a bluff body with moving boundary is developed. The program is verified by two-dimensional square cavity driving flow and Taylor vortex train problem respectively. The stability and the accuracy of time calculation.
5. Numerical analysis of the flow around a vibrating roof. The following closed large-span flat roof structure is studied. The numerical simulation of the flow around the roof under the second harmonic mode vibration is carried out by using the program developed in this paper. The vibration of the roof is studied by comparing with the results of the flow around a rigid roof structure of the same size. The results show that the roof vibration is an important factor affecting the average and fluctuating wind pressure coefficients on the surface of the structure; the vibration of the roof results in the complexity of the vortex structure around the flow field and the increase of the characteristic turbulence; the vibration of the roof has an obvious effect on the instantaneous wind pressure distribution around the flow field. The second-order harmonic modes are liable to cause the resonance between the fluctuating wind and the roof, which is not conducive to the wind stability of the roof.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU312.1
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