Physics:Green's function number

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In mathematical heat conduction, the Green's function number is used to uniquely categorize certain fundamental solutions of the heat equation to make existing solutions easier to identify, store, and retrieve.

Background

Numbers have long been used to identify types of boundary conditions.[1][2][3] The Green's function number system was proposed by Beck and Litkouhi in 1988[4] and has seen increasing use since then.[5][6][7][8] The number system has been used to catalog a large collection of Green's functions and related solutions.[9][10][11][12]

Although the examples given below are for the heat equation, this number system applies to any phenomena described by differential equations such as diffusion, acoustics, electromagnetics, fluid dynamics, etc.

Notation

The Green's function number specifies the coordinate system and the type of boundary conditions that a Green's function satisfies. The Green's function number has two parts, a letter designation followed by a number designation. The letter(s) designate the coordinate system, while the numbers designate the type of boundary conditions that are satisfied.

Table 1. Boundary conditions designations for Green's function number system.
Name Boundary condition Number
No physical boundary G is bounded 0
Dirichlet [math]\displaystyle{ G = 0 }[/math] 1
Neumann [math]\displaystyle{ \frac{\partial G}{\partial n} = 0 }[/math] 2
Robin [math]\displaystyle{ k \frac{\partial G}{\partial n} + h G= 0 }[/math] 3

Some of the designations for the Greens function number system are given next. Coordinate system designations include: X, Y, and Z for Cartesian coordinates; R, Z, [math]\displaystyle{ \phi }[/math] for cylindrical coordinates; and, RS, [math]\displaystyle{ \phi }[/math], [math]\displaystyle{ \theta }[/math] for spherical coordinates. Designations for several boundary conditions are given in Table 1. The zeroth boundary condition is important for identifying the presence of a coordinate boundary where no physical boundary exists, for example, far away in a semi-infinite body or at the center of a cylindrical or spherical body.

Examples in Cartesian coordinates

X11

As an example, number X11 denotes the Green's function that satisfies the heat equation in the domain (0 < x < L) for boundary conditions of type 1 (Dirichlet) at both boundaries x = 0 and x = L. Here X denotes the Cartesian coordinate and 11 denotes the type 1 boundary condition at both sides of the body. The boundary value problem for the X11 Green's function is given by

[math]\displaystyle{ \begin{align} \dfrac{\partial^2 G}{\partial x^2} +\dfrac{1}{\alpha} \delta(t - \tau) \delta(x - x') = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; &\;\; 0 \lt x \lt L; \;\;\; t\gt 0 \\ G |_{x=0}=0; \;\; G |_{x=L}=0; \;\; G |_{t\lt \tau}=0. & \end{align} }[/math]

Here [math]\displaystyle{ \alpha }[/math] is the thermal diffusivity (m2/s) and [math]\displaystyle{ \delta }[/math] is the Dirac delta function. This GF is developed elsewhere. [13] [14]

X20

As another Cartesian example, number X20 denotes the Green's function in the semi-infinite body ([math]\displaystyle{ 0\lt x\lt \infty }[/math]) with a Neumann (type 2) boundary at x = 0. Here X denotes the Cartesian coordinate, 2 denotes the type 2 boundary condition at x = 0 and 0 denotes the zeroth type boundary condition (boundedness) at [math]\displaystyle{ x = \infty }[/math]. The boundary value problem for the X20 Green's function is given by

[math]\displaystyle{ \begin{align} \dfrac{\partial^2 G}{\partial x^2} +\dfrac{1}{\alpha} \delta(t - \tau) \delta(x - x') = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; & \;\; 0 \lt x \lt \infty; \;\;\; t\gt 0 \\ \dfrac{\partial G}{\partial n} |_{x=0}=0; \;\; G |_{x\rightarrow \infty} \mbox{ is bounded}; \;\; G |_{t\lt \tau}=0. & \end{align} }[/math]

This GF is published elsewhere. [15] [16]

X10Y20

As a two-dimensional example, number X10Y20 denotes the Green's function in the quarter-infinite body ([math]\displaystyle{ 0\lt x\lt \infty }[/math], [math]\displaystyle{ 0\lt y\lt \infty }[/math]) with a Dirichlet (type 1) boundary at x = 0 and a Neumann (type 2) boundary at y = 0. The boundary value problem for the X10Y20 Green's function is given by

[math]\displaystyle{ \begin{align} \dfrac{\partial^2 G}{\partial x^2} +\dfrac{\partial^2 G}{\partial y^2} +\dfrac{1}{\alpha} \delta(t - \tau) \delta(x - x') \delta(y - y') = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; & \;\; 0 \lt x \lt \infty; \;\; 0 \lt y \lt \infty; \;\;\; t\gt 0 \\ G |_{x=0} = 0; \;\; \dfrac{\partial G}{\partial n} |_{y=0}=0; \;\; & \\ G |_{x\rightarrow \infty} \mbox{ is bounded}; \;\; G |_{y\rightarrow \infty} \mbox{ is bounded}; \;\; G |_{t\lt \tau}=0. & \end{align} }[/math]

Applications of related half-space and quarter-space GF are available. [17]

Examples in cylindrical coordinates

R03

As an example in the cylindrical coordinate system, number R03 denotes the Green's function that satisfies the heat equation in the solid cylinder (0 < r < a) with a boundary condition of type 3 (Robin) at r = a. Here letter R denotes the cylindrical coordinate system, number 0 denotes the zeroth boundary condition (boundedness) at the center of the cylinder (r = 0), and number 3 denotes the type 3 (Robin) boundary condition at r = a. The boundary value problem for R03 Green's function is given by

[math]\displaystyle{ \dfrac{1}{r}\dfrac{\partial}{\partial r} \left( r \dfrac{\partial G}{\partial r} \right) +\dfrac{1}{\alpha} \delta(t - \tau) \dfrac{\delta(r - r')}{2 \pi r'} = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; \;\; 0 \lt r \lt a; \;\;\; t\gt 0 }[/math]
[math]\displaystyle{ G |_{r=0} \mbox{ is bounded}; \;\;k \dfrac{\partial G}{\partial n} |_{r=a} + hG |_{r=a} =0; \;\; G |_{t\lt \tau}=0. }[/math]

Here [math]\displaystyle{ k }[/math] is thermal conductivity (W/(m K)) and [math]\displaystyle{ h }[/math] is the heat transfer coefficient (W/(m2 K)). See [18] [19] for this GF.

R10

As another example, number R10 denotes the Green's function in a large body containing a cylindrical void (a < r < [math]\displaystyle{ \infty }[/math]) with a type 1 (Dirichlet) boundary condition at r = a. Again letter R denotes the cylindrical coordinate system, number 1 denotes the type 1 boundary at r = a, and number 0 denotes the type zero boundary (boundedness) at large values of r. The boundary value problem for the R10 Green's function is given by

[math]\displaystyle{ \begin{align} \dfrac{1}{r}\dfrac{\partial}{\partial r} \left( r \dfrac{\partial G}{\partial r} \right) +\dfrac{1}{\alpha} \delta(t - \tau) \dfrac{\delta(r - r')}{2 \pi r'} = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; &\;\; a \lt r \lt \infty; \;\;\; t\gt 0 \\ G |_{r=a} = 0; \;\;G |_{r\rightarrow \infty} \mbox{ is bounded}; \;\; G |_{t\lt \tau}=0. & \end{align} }[/math]

This GF is available elsewhere. [20] [21]

R01πœ™00

As a two dimensional example, number R01[math]\displaystyle{ \phi }[/math]00 denotes the Green's function in a solid cylinder with angular dependence, with a type 1 (Dirichlet) boundary condition at r = a. Here letter [math]\displaystyle{ \phi }[/math] denotes the angular coordinate, and numbers 00 denote the type zero boundaries for angle; here no physical boundary takes the form of the periodic boundary condition. The boundary value problem for the R01[math]\displaystyle{ \phi }[/math]00 Green's function is given by

[math]\displaystyle{ \begin{align} \dfrac{1}{r}\dfrac{\partial}{\partial r} \left( r \dfrac{\partial G}{\partial r} \right) + \dfrac{1}{r^2}\dfrac{\partial^2 G}{\partial \phi^2} + \dfrac{1}{\alpha} \delta(t - \tau) \dfrac{\delta(r - r')}{2 \pi r'} \delta(\phi - \phi ') = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; &\;\; 0 \lt r \lt a; \;\;\; 0\lt \phi \lt 2\pi; \;\;\; t\gt 0 \\ G |_{r=0} \mbox{ is bounded,} \;\;G |_{r=a} =0; &\\ G |_{\phi=0} = G |_{\phi=2 \pi}; \dfrac{\partial G}{\partial \phi}|_{\phi=0} = \dfrac{\partial G}{\partial \phi} |_{\phi=2 \pi}; \;\; G |_{t\lt \tau}=0. & \end{align} }[/math]

Both a transient [22] and steady form [23] of this GF are available.

Example in spherical coordinates

RS02

As an example in the spherical coordinate system, number RS02 denotes the Green's function for a solid sphere (0 < r < b ) with a type 2 (Neumann) boundary condition at r = b. Here letters RS denote the radial-spherical coordinate system, number 0 denotes the zeroth boundary condition (boundedness) at r=0, and number 2 denotes the type 2 boundary at r = b. The boundary value problem for the RS02 Green's function is given by

[math]\displaystyle{ \dfrac{1}{r^2}\dfrac{\partial}{\partial r} \left( r^2 \dfrac{\partial G}{\partial r} \right) +\dfrac{1}{\alpha} \delta(t - \tau) \dfrac{\delta(r - r')}{4 \pi r^2} = \dfrac{1}{\alpha} \dfrac{\partial G}{\partial t}; \;\; 0 \lt r \lt b; \;\;\; t\gt 0 }[/math]
[math]\displaystyle{ G |_{r=0} \mbox{ is bounded}; \;\; \dfrac{\partial G}{\partial n} |_{r=b} =0; \;\; G |_{t\lt \tau}=0. }[/math]

This GF is available elsewhere. [24]

See also

References

  1. ↑ Luikov, A. V. (1968). Analytical Heat Diffusion Theory. doi:10.1016/B978-0-12-459756-3.X5001-9. ISBN 0124597564. 
  2. ↑ Γ–zışık, M. Necati (1980). Heat conduction (1st ed.). New York: Wiley. ISBN 047105481X. 
  3. ↑ Nowak, A.; BiaΕ‚ecki, R.; Kurpisz, K. (February 1987). "Evaluating eigenvalues for boundary value problems of heat conduction in rectangular and cylindrical co-ordinate systems". International Journal for Numerical Methods in Engineering 24 (2): 419–445. doi:10.1002/nme.1620240210. 
  4. ↑ Beck, James V.; Litkouhi, Bahman (March 1988). "Heat conduction numbering system for basic geometries". International Journal of Heat and Mass Transfer 31 (3): 505–515. doi:10.1016/0017-9310(88)90032-4. 
  5. ↑ Al-Nimr, M. A.; Alkam, M. K. (19 September 1997). "A generalized thermal boundary condition". Heat and Mass Transfer 33 (1–2): 157–161. doi:10.1007/s002310050173. 
  6. ↑ de Monte, Filippo (September 2006). "Multi-layer transient heat conduction using transition time scales". International Journal of Thermal Sciences 45 (9): 882–892. doi:10.1016/j.ijthermalsci.2005.11.006. 
  7. ↑ Lefebvre, G. (December 2010). "A general modal-based numerical simulation of transient heat conduction in a one-dimensional homogeneous slab". Energy and Buildings 42 (12): 2309–2322. doi:10.1016/j.enbuild.2010.07.024. 
  8. ↑ Toptan, A.; Porter, N. W.; Hales, J. D. (2020). "Construction of a code verification matrix for heat conduction with finite element code applications". Journal of Verification, Validation and Uncertainty Quantification 5 (4): 041002. doi:10.1115/1.4049037. 
  9. ↑ Cole, Kevin; Beck, James; Haji-Sheikh, A.; Litkouhi, Bahman (16 July 2010). Heat Conduction Using Greens Functions. doi:10.1201/9781439895214. ISBN 9781439813546. 
  10. ↑ Green's Function Library, https://www.engr.unl.edu/~glibrary/home/index.html
  11. ↑ "Green's Function Library". https://www.engr.unl.edu/~glibrary/home/index.html. 
  12. ↑ "Exact Analytical Conduction Toolbox". http://exact.unl.edu/. 
  13. ↑ Luikov, A. V. (1968). Analytical Heat Diffusion Theory. Academic Press. p. 388. ISBN 0124597564. 
  14. ↑ Cole, K. D.; Beck, J. V.; Haji-Sheikh, A.; Litkouhi, B. (2011). Heat Conduction using Green's Functions (2nd ed.). Boca Rotan, FL: Taylor and Francis. p. 119. doi:10.1201/9781439895214. ISBN 9780429109188. 
  15. ↑ Luikov, A. V. (1968). Analytical Heat Diffusion Theory. Academic Press. p. 387. ISBN 0124597564. 
  16. ↑ Carslaw, H. S.; Jaeger, J. C. (1959). Conduction of Heat in Solids. Oxford University Press. p. 276. ISBN 9780198533689. 
  17. ↑ Beck, J. V.; Wright, N..; Haji-Sheikh, A.; Cole, K. D; Amos. D. (2008). "Conduction in rectangular plates with boundary temperatures specified". International Journal of Heat and Mass Transfer 52 (19–20): 4676–4690. doi:10.1016/j.ijheatmasstransfer.2008.02.020. https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1036&context=mechengfacpub. 
  18. ↑ Carslaw, H. S.; Jaeger, J. C. (1959). Conduction of Heat in Solids. Oxford University Press. p. 369. ISBN 9780198533689. 
  19. ↑ Cole, K. D.; Beck, J. V.; Haji_Sheikh, A.; Litkouhi, B. (2011). Heat Conduction Using Green's Functions (2nd ed.). Boca Rotan, FL: Taylor and Francis. p. 543. doi:10.1201/9781439895214. ISBN 9780429109188. 
  20. ↑ Carslaw, H. S.; Jaeger, J. C. (1959). Conduction of Heat in Solids. Oxford University Press. p. 378. ISBN 9780198533689. 
  21. ↑ Thambynayagam, R. K. M. (2011). The Diffusion Handbook. McGraw Hill. p. 432. ISBN 9780071751841. 
  22. ↑ Cole, K. D.; Beck, J. V.; Haji_Sheikh, A.; Litkouhi, B. (2011). Heat Conduction Using Green's Functions (2nd ed.). Boca Rotan, FL: Taylor and Francis. p. 554. doi:10.1201/9781439895214. ISBN 9780429109188. 
  23. ↑ Melnikov, Y. A. (1999). Influence Functions and Matrices. New York: Marcel Dekker. p. 223. ISBN 9780824719418. 
  24. ↑ Cole, K. D.; Beck, J. V.; Haji_Sheikh, A.; Litkouhi, B. (2011). Heat Conduction Using Green's Functions (2nd ed.). Boca Rotan, FL: Taylor and Francis. p. 309. doi:10.1201/9781439895214. ISBN 9780429109188. 



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