CFD湍流模型使用技巧培训
相关主题
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
人造湍流发生器
涡方法（Fluent） 谐波湍流发生器（HTG）（CFX）
Unsteady Models
URANS
URANS gives unphysical single mode unsteady behavior
LES (Large Eddy Simulation)
Too expensive for most industrial flows due to high resolution requirements in boundary layers
Higher order models • EARSM – w • SMC - w
Extensions •Stagnation point •Curvature correction •Rough walls •Reattachment correction
Menter’s SST k-w Model
,
1020
k-w model transformed from std. k-3 model
k 2
WMiolcdoifxie’ odrWigiinlcaol xk-kw-wmmodoedlel
F1 1 F1 0
in the inner layer in the outler layer
Wall
SRS尺度解析模拟模型
尺度自适应模拟（SAS）SAS-SST模型（Fluent，CFX） 分离涡模拟（DES）模型
DES-SA(DDES)模型（Fluent） DES-SST（DDES）模型（Fluent，CFX） Relizable k-ε-DES模型（Fluent）
大涡模拟（LES）
• CFD湍流模型使用技巧培训
CFD湍流模型使用技巧培训
目录
ANSYS CFD 湍流模型新发展 ANSYS CFD 湍流模型使用技巧 ANSYS CFD 湍流模型验证案例
Flow Separation
Corner Vortices
图片 大图
Transition
NASA X-29
Unsteady Effects
• Numerous developments: – Correlation based models – Low-Re models – en linear stability –… – DNS
Transition Modelling
Low-Re models (only bypass transition) Based on transport equations for e.g. k and (compatible with modern CFD codes) Cannot be calibrated independently of viscous sublayer model Poor accuracy and robustness – not used in industry
SAS – globally unstable flows DDES – globally and locally unstable flows ELES/WMLES marginally unstable flows
ANSYS Fluent 湍流模型
RANS Models
One-Equation Model Spalart-Allmaras
DES/SAS Large Eddy Simulation
Increase in computational cost
ANSYS CFX 湍流模型
A large number of turbulence models are available in CFX, some have very specific applications while others can be applied to a wider class of flows with a reasonable degree of confidence
Eddy Simulation Models:
Large Eddy Simulation (LES) [transient]
Detached Eddy Simulation (DES)* Scale Adaptive Simulation SST (SAS)*
* Not available in the ANSYS CFD-Flo product
嵌入式大涡模拟
– 可以和DES/SAS模型联用
E-LES: Spatially decaying turbulence
E-LES: Fully developed channel flow
RANS
Re=395
LES
Viscosity ratio on iso-surfaces of
q-criterion (-500)
Transition Modelling
Effects
• Re number effects • Heat transfer • Wall shear stress • Separation behaviour • Efficiency of many technical
devices
Modelling
Smagorinsky-Lilly模型（+dynamic）(Fluent，CFX) WALE模型（Fluent，CFX） 动能次网格动态模型(Fluent) Algebraic Wall Modeled LES (WMLES) (Fluent, CFX)
嵌入式LES（ELES）模型
所有RANS模型和所有非动态LES模型的组合（Fluent） 强制分区模型(CFX)
Two-Equation Models Standard k–ε RNG k–ε Realizable k–ε Standard k–ω SST k–ω
k-kl-w Transition Model (3 eq.) SST Transition Model (4 eq.) 4-Equation v2f Model Reynolds Stress Model Detached Eddy Simulation
F1
Dk Dt
in n er
1
F1
Dk Dt
o u ter
F1 1 1 F1 2
where , k , w ,g
F1 tanh arg14
arg1
min
max
k *w
y
,
500 y2w
,
4w2 k CDkw y2
CDkw
max
2
w
2
1 w
k x j
w x j
The two sets of equations and the model constants are blended in such
a way that the resulting equation set transitions smoothly from one
equation to another.
Switch of model
Based on ratio of turbulent length-scale to grid size Different numerical treatment in RANS and LES regions
RANS
Lt c
?
LES
Lt c
Embedded LES
Correlation based model Reasonably accurate Correlations can be found for many different transition mechanisms (e.g. FSTI, dp/dx, Roughness) Not compatible with 3D flows and unstructured/parallel CFD codes – non-local
Mean velocity values inside LES zone.
目录
ANSYS CFD 湍流模型新发展 ANSYS CFD 湍流模型使用技巧 ANSYS CFD 湍流模型验证案例
Industrial Turbulent Flows
eN method (only natural transition) Very accurate predictions for 2D airfoils (low FSTI) N-S codes are not accurate enough to evaluate stability equations Extension to generic 3D flows very difficult (impossible?) Cannot account of non-linear effects (e.g. high FSTI, roughness)
RANS Eddy-viscosity Models:
RANS Reynolds-Stress Models:
Zero Equation model.
LRR Reynolds Stress
SA model
QI Reynolds Stress
Standard k-ε model.
Speziale, Sarkar and Gatski Reynolds
Transition Modelling
Two Transport Equations Intermittency (g) Equation Fraction of turbulent vs laminar flow Transition onset controlled by relation between vorticity Reynolds number and Reθt Transition Onset Reynolds number Equation Used to pass information about freestream conditions into b.l. e.g. impinging wakes
RNG k-ε model.
Stress
Standard k-ω model.
SMC-ω model
Baseline (BSL) zonal k-ω based model. Baseline (BSL) Reynolds' Stress model
SST zonal k-ω based model. (k-ε)1E model.
Integration Platform w-equation
2-equation models • k-w, BSL, SST
Transition Model • Baidu Nhomakorabea-ReQ model
Unsteady models • SST-SAS • SST-DES
w-equation
Wall Treatment • Automatic wall treatment
SAS (Scale-Adaptive Simulation)
Extends URANS to many technical flows Provides “LES”-content in unsteady regions.
Hybrid Models
Hybrid Model
RANS equations in bl LES detached “regions”
Flow Reattachment Mixing /combustion Vortical Flows
ANSYS CFD 湍流模型新发展
RANS modelling key to industrial CFD Laminar-turbulent Transition modelling Scale-Resolving Simulation (SRS)
DES (Detached Eddy Simulation)
First industrial-strength model for high-Re with LEScontent
Increased complexity (grid sensitivity) due to explicit mix of to modelling concepts
涡方法（Fluent） 谐波湍流发生器（HTG）（CFX）
Unsteady Models
URANS
URANS gives unphysical single mode unsteady behavior
LES (Large Eddy Simulation)
Too expensive for most industrial flows due to high resolution requirements in boundary layers
Higher order models • EARSM – w • SMC - w
Extensions •Stagnation point •Curvature correction •Rough walls •Reattachment correction
Menter’s SST k-w Model
,
1020
k-w model transformed from std. k-3 model
k 2
WMiolcdoifxie’ odrWigiinlcaol xk-kw-wmmodoedlel
F1 1 F1 0
in the inner layer in the outler layer
Wall
SRS尺度解析模拟模型
尺度自适应模拟（SAS）SAS-SST模型（Fluent，CFX） 分离涡模拟（DES）模型
DES-SA(DDES)模型（Fluent） DES-SST（DDES）模型（Fluent，CFX） Relizable k-ε-DES模型（Fluent）
大涡模拟（LES）
• CFD湍流模型使用技巧培训
CFD湍流模型使用技巧培训
目录
ANSYS CFD 湍流模型新发展 ANSYS CFD 湍流模型使用技巧 ANSYS CFD 湍流模型验证案例
Flow Separation
Corner Vortices
图片 大图
Transition
NASA X-29
Unsteady Effects
• Numerous developments: – Correlation based models – Low-Re models – en linear stability –… – DNS
Transition Modelling
Low-Re models (only bypass transition) Based on transport equations for e.g. k and (compatible with modern CFD codes) Cannot be calibrated independently of viscous sublayer model Poor accuracy and robustness – not used in industry
SAS – globally unstable flows DDES – globally and locally unstable flows ELES/WMLES marginally unstable flows
ANSYS Fluent 湍流模型
RANS Models
One-Equation Model Spalart-Allmaras
DES/SAS Large Eddy Simulation
Increase in computational cost
ANSYS CFX 湍流模型
A large number of turbulence models are available in CFX, some have very specific applications while others can be applied to a wider class of flows with a reasonable degree of confidence
Eddy Simulation Models:
Large Eddy Simulation (LES) [transient]
Detached Eddy Simulation (DES)* Scale Adaptive Simulation SST (SAS)*
* Not available in the ANSYS CFD-Flo product
嵌入式大涡模拟
– 可以和DES/SAS模型联用
E-LES: Spatially decaying turbulence
E-LES: Fully developed channel flow
RANS
Re=395
LES
Viscosity ratio on iso-surfaces of
q-criterion (-500)
Transition Modelling
Effects
• Re number effects • Heat transfer • Wall shear stress • Separation behaviour • Efficiency of many technical
devices
Modelling
Smagorinsky-Lilly模型（+dynamic）(Fluent，CFX) WALE模型（Fluent，CFX） 动能次网格动态模型(Fluent) Algebraic Wall Modeled LES (WMLES) (Fluent, CFX)
嵌入式LES（ELES）模型
所有RANS模型和所有非动态LES模型的组合（Fluent） 强制分区模型(CFX)
Two-Equation Models Standard k–ε RNG k–ε Realizable k–ε Standard k–ω SST k–ω
k-kl-w Transition Model (3 eq.) SST Transition Model (4 eq.) 4-Equation v2f Model Reynolds Stress Model Detached Eddy Simulation
F1
Dk Dt
in n er
1
F1
Dk Dt
o u ter
F1 1 1 F1 2
where , k , w ,g
F1 tanh arg14
arg1
min
max
k *w
y
,
500 y2w
,
4w2 k CDkw y2
CDkw
max
2
w
2
1 w
k x j
w x j
The two sets of equations and the model constants are blended in such
a way that the resulting equation set transitions smoothly from one
equation to another.
Switch of model
Based on ratio of turbulent length-scale to grid size Different numerical treatment in RANS and LES regions
RANS
Lt c
?
LES
Lt c
Embedded LES
Correlation based model Reasonably accurate Correlations can be found for many different transition mechanisms (e.g. FSTI, dp/dx, Roughness) Not compatible with 3D flows and unstructured/parallel CFD codes – non-local
Mean velocity values inside LES zone.
目录
ANSYS CFD 湍流模型新发展 ANSYS CFD 湍流模型使用技巧 ANSYS CFD 湍流模型验证案例
Industrial Turbulent Flows
eN method (only natural transition) Very accurate predictions for 2D airfoils (low FSTI) N-S codes are not accurate enough to evaluate stability equations Extension to generic 3D flows very difficult (impossible?) Cannot account of non-linear effects (e.g. high FSTI, roughness)
RANS Eddy-viscosity Models:
RANS Reynolds-Stress Models:
Zero Equation model.
LRR Reynolds Stress
SA model
QI Reynolds Stress
Standard k-ε model.
Speziale, Sarkar and Gatski Reynolds
Transition Modelling
Two Transport Equations Intermittency (g) Equation Fraction of turbulent vs laminar flow Transition onset controlled by relation between vorticity Reynolds number and Reθt Transition Onset Reynolds number Equation Used to pass information about freestream conditions into b.l. e.g. impinging wakes
RNG k-ε model.
Stress
Standard k-ω model.
SMC-ω model
Baseline (BSL) zonal k-ω based model. Baseline (BSL) Reynolds' Stress model
SST zonal k-ω based model. (k-ε)1E model.
Integration Platform w-equation
2-equation models • k-w, BSL, SST
Transition Model • Baidu Nhomakorabea-ReQ model
Unsteady models • SST-SAS • SST-DES
w-equation
Wall Treatment • Automatic wall treatment
SAS (Scale-Adaptive Simulation)
Extends URANS to many technical flows Provides “LES”-content in unsteady regions.
Hybrid Models
Hybrid Model
RANS equations in bl LES detached “regions”
Flow Reattachment Mixing /combustion Vortical Flows
ANSYS CFD 湍流模型新发展
RANS modelling key to industrial CFD Laminar-turbulent Transition modelling Scale-Resolving Simulation (SRS)
DES (Detached Eddy Simulation)
First industrial-strength model for high-Re with LEScontent
Increased complexity (grid sensitivity) due to explicit mix of to modelling concepts