Del in cylindrical and spherical coordinates

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This is a list of some vector calculus formulae for working with common curvilinear coordinate systems.

Notes

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  • This article uses the standard notation ISO 80000-2, which supersedes ISO 31-11, for spherical coordinates (other sources may reverse the definitions of θ and φ):
    • The polar angle is denoted by θ[0,π]: it is the angle between the z-axis and the radial vector connecting the origin to the point in question.
    • The azimuthal angle is denoted by φ[0,2π]: it is the angle between the x-axis and the projection of the radial vector onto the xy-plane.
  • The function atan2(y, x) can be used instead of the mathematical function arctan(y/x) owing to its domain and image. The classical arctan function has an image of (−π/2, +π/2), whereas atan2 is defined to have an image of (−π, π].

Coordinate conversions

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Conversion between Cartesian, cylindrical, and spherical coordinates[1]
From
Cartesian Cylindrical Spherical
To Cartesian x=xy=yz=z x=ρcosφy=ρsinφz=z x=rsinθcosφy=rsinθsinφz=rcosθ
Cylindrical ρ=x2+y2φ=arctan(yx)z=z ρ=ρφ=φz=z ρ=rsinθφ=φz=rcosθ
Spherical r=x2+y2+z2θ=arccos(zx2+y2+z2)φ=arctan(yx) r=ρ2+z2θ=arctan(ρz)φ=φ r=rθ=θφ=φ

Note that the operation arctan(AB) must be interpreted as the two-argument inverse tangent, atan2.

Unit vector conversions

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Conversion between unit vectors in Cartesian, cylindrical, and spherical coordinate systems in terms of destination coordinates[1]
Cartesian Cylindrical Spherical
Cartesian 𝐱^=𝐱^𝐲^=𝐲^𝐳^=𝐳^ 𝐱^=cosφ𝝆^sinφ𝝋^𝐲^=sinφ𝝆^+cosφ𝝋^𝐳^=𝐳^ 𝐱^=sinθcosφ𝐫^+cosθcosφ𝜽^sinφ𝝋^𝐲^=sinθsinφ𝐫^+cosθsinφ𝜽^+cosφ𝝋^𝐳^=cosθ𝐫^sinθ𝜽^
Cylindrical 𝝆^=x𝐱^+y𝐲^x2+y2𝝋^=y𝐱^+x𝐲^x2+y2𝐳^=𝐳^ 𝝆^=𝝆^𝝋^=𝝋^𝐳^=𝐳^ 𝝆^=sinθ𝐫^+cosθ𝜽^𝝋^=𝝋^𝐳^=cosθ𝐫^sinθ𝜽^
Spherical 𝐫^=x𝐱^+y𝐲^+z𝐳^x2+y2+z2𝜽^=(x𝐱^+y𝐲^)z(x2+y2)𝐳^x2+y2+z2x2+y2𝝋^=y𝐱^+x𝐲^x2+y2 𝐫^=ρ𝝆^+z𝐳^ρ2+z2𝜽^=z𝝆^ρ𝐳^ρ2+z2𝝋^=𝝋^ 𝐫^=𝐫^𝜽^=𝜽^𝝋^=𝝋^
Conversion between unit vectors in Cartesian, cylindrical, and spherical coordinate systems in terms of source coordinates
Cartesian Cylindrical Spherical
Cartesian 𝐱^=𝐱^𝐲^=𝐲^𝐳^=𝐳^ 𝐱^=x𝝆^y𝝋^x2+y2𝐲^=y𝝆^+x𝝋^x2+y2𝐳^=𝐳^ 𝐱^=x(x2+y2𝐫^+z𝜽^)yx2+y2+z2𝝋^x2+y2x2+y2+z2𝐲^=y(x2+y2𝐫^+z𝜽^)+xx2+y2+z2𝝋^x2+y2x2+y2+z2𝐳^=z𝐫^x2+y2𝜽^x2+y2+z2
Cylindrical 𝝆^=cosφ𝐱^+sinφ𝐲^𝝋^=sinφ𝐱^+cosφ𝐲^𝐳^=𝐳^ 𝝆^=𝝆^𝝋^=𝝋^𝐳^=𝐳^ 𝝆^=ρ𝐫^+z𝜽^ρ2+z2𝝋^=𝝋^𝐳^=z𝐫^ρ𝜽^ρ2+z2
Spherical 𝐫^=sinθ(cosφ𝐱^+sinφ𝐲^)+cosθ𝐳^𝜽^=cosθ(cosφ𝐱^+sinφ𝐲^)sinθ𝐳^𝝋^=sinφ𝐱^+cosφ𝐲^ 𝐫^=sinθ𝝆^+cosθ𝐳^𝜽^=cosθ𝝆^sinθ𝐳^𝝋^=𝝋^ 𝐫^=𝐫^𝜽^=𝜽^𝝋^=𝝋^

Del formula

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Table with the del operator in cartesian, cylindrical and spherical coordinates
Operation Cartesian coordinates (x, y, z) Cylindrical coordinates (ρ, φ, z) Spherical coordinates (r, θ, φ),
where θ is the polar angle and φ is the azimuthal angleα
Vector field A Ax𝐱^+Ay𝐲^+Az𝐳^ Aρ𝝆^+Aφ𝝋^+Az𝐳^ Ar𝐫^+Aθ𝜽^+Aφ𝝋^
Gradient f[1] fx𝐱^+fy𝐲^+fz𝐳^ fρ𝝆^+1ρfφ𝝋^+fz𝐳^ fr𝐫^+1rfθ𝜽^+1rsinθfφ𝝋^
Divergence ∇ ⋅ A[1] Axx+Ayy+Azz 1ρ(ρAρ)ρ+1ρAφφ+Azz 1r2(r2Ar)r+1rsinθθ(Aθsinθ)+1rsinθAφφ
Curl ∇ × A[1] (AzyAyz)𝐱^+(AxzAzx)𝐲^+(AyxAxy)𝐳^ (1ρAzφAφz)𝝆^+(AρzAzρ)𝝋^+1ρ((ρAφ)ρAρφ)𝐳^ 1rsinθ(θ(Aφsinθ)Aθφ)𝐫^+1r(1sinθArφr(rAφ))𝜽^+1r(r(rAθ)Arθ)𝝋^
Laplace operator 2f ≡ ∆f[1] 2fx2+2fy2+2fz2 1ρρ(ρfρ)+1ρ22fφ2+2fz2 1r2r(r2fr)+1r2sinθθ(sinθfθ)+1r2sin2θ2fφ2
Vector gradient Aβ Axx𝐱^𝐱^+Axy𝐱^𝐲^+Axz𝐱^𝐳^+Ayx𝐲^𝐱^+Ayy𝐲^𝐲^+Ayz𝐲^𝐳^+Azx𝐳^𝐱^+Azy𝐳^𝐲^+Azz𝐳^𝐳^ Aρρ𝝆^𝝆^+(1ρAρφAφρ)𝝆^𝝋^+Aρz𝝆^𝐳^+Aφρ𝝋^𝝆^+(1ρAφφ+Aρρ)𝝋^𝝋^+Aφz𝝋^𝐳^+Azρ𝐳^𝝆^+1ρAzφ𝐳^𝝋^+Azz𝐳^𝐳^ Arr𝐫^𝐫^+(1rArθAθr)𝐫^𝜽^+(1rsinθArφAφr)𝐫^𝝋^+Aθr𝜽^𝐫^+(1rAθθ+Arr)𝜽^𝜽^+(1rsinθAθφcotθAφr)𝜽^𝝋^+Aφr𝝋^𝐫^+1rAφθ𝝋^𝜽^+(1rsinθAφφ+cotθAθr+Arr)𝝋^𝝋^
Vector Laplacian 2A ≡ ∆A[2] 2Ax𝐱^+2Ay𝐲^+2Az𝐳^

(2AρAρρ22ρ2Aφφ)𝝆^+(2AφAφρ2+2ρ2Aρφ)𝝋^+2Az𝐳^

(2Ar2Arr22r2sinθ(Aθsinθ)θ2r2sinθAφφ)𝐫^+(2AθAθr2sin2θ+2r2Arθ2cosθr2sin2θAφφ)𝜽^+(2AφAφr2sin2θ+2r2sinθArφ+2cosθr2sin2θAθφ)𝝋^

Directional derivative (A ⋅ ∇)B[3] 𝐀Bx𝐱^+𝐀By𝐲^+𝐀Bz𝐳^ (AρBρρ+AφρBρφ+AzBρzAφBφρ)𝝆^+(AρBφρ+AφρBφφ+AzBφz+AφBρρ)𝝋^+(AρBzρ+AφρBzφ+AzBzz)𝐳^

(ArBrr+AθrBrθ+AφrsinθBrφAθBθ+AφBφr)𝐫^+(ArBθr+AθrBθθ+AφrsinθBθφ+AθBrrAφBφcotθr)𝜽^+(ArBφr+AθrBφθ+AφrsinθBφφ+AφBrr+AφBθcotθr)𝝋^

Tensor divergence ∇ ⋅ Tγ

(Txxx+Tyxy+Tzxz)𝐱^+(Txyx+Tyyy+Tzyz)𝐲^+(Txzx+Tyzy+Tzzz)𝐳^

[Tρρρ+1ρTφρφ+Tzρz+1ρ(TρρTφφ)]𝝆^+[Tρφρ+1ρTφφφ+Tzφz+1ρ(Tρφ+Tφρ)]𝝋^+[Tρzρ+1ρTφzφ+Tzzz+Tρzρ]𝐳^

[Trrr+2Trrr+1rTθrθ+cotθrTθr+1rsinθTφrφ1r(Tθθ+Tφφ)]𝐫^+[Trθr+2Trθr+1rTθθθ+cotθrTθθ+1rsinθTφθφ+TθrrcotθrTφφ]𝜽^+[Trφr+2Trφr+1rTθφθ+1rsinθTφφφ+Tφrr+cotθr(Tθφ+Tφθ)]𝝋^

  • This page uses θ for the polar angle and φ for the azimuthal angle, which is common notation in physics. The source that is used for these formulae uses θ for the azimuthal angle and φ for the polar angle, which is common mathematical notation. In order to get the mathematics formulae, switch θ and φ in the formulae shown in the table above.
  • Defined in Cartesian coordinates as i𝐀𝐞i. An alternative definition is 𝐞ii𝐀.
  • Defined in Cartesian coordinates as 𝐞ii𝐓. An alternative definition is i𝐓𝐞i.

Differential elements

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Operation Cartesian coordinates
(x, y, z)
Cylindrical coordinates
(ρ, φ, z)
Spherical coordinatesα
(r, θ, φ)
Differential displacement d[1] dx𝐱^+dy𝐲^+dz𝐳^ dρ𝝆^+ρdφ𝝋^+dz𝐳^ dr𝐫^+rdθ𝜽^+rsinθdφ𝝋^
Differential normal area dS dydz𝐱^+dxdz𝐲^+dxdy𝐳^ ρdφdz𝝆^+dρdz𝝋^+ρdρdφ𝐳^ r2sinθdθdφ𝐫^+rsinθdrdφ𝜽^+rdrdθ𝝋^
Differential volume dV[1] dxdydz ρdρdφdz r2sinθdrdθdφ

Calculation rules

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  1. divgradff2f
  2. curlgradf×f=𝟎
  3. divcurl𝐀(×𝐀)=0
  4. curlcurl𝐀×(×𝐀)=(𝐀)2𝐀 (Lagrange's formula for del)
  5. 2(fg)=f2g+2fg+g2f
  6. 2(𝐏𝐐)=𝐐2𝐏𝐏2𝐐+2[(𝐏)𝐐+𝐏××𝐐] (From [4] )

Cartesian derivation

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File:Nabla cartesian.svg

div𝐀=limV0V𝐀d𝐒VdV=[Ax(x+dx)Ax(x)]dydz+[Ay(y+dy)Ay(y)]dxdz+[Az(z+dz)Az(z)]dxdydxdydz=Axx+Ayy+Azz

(curl𝐀)x=limS𝐱^0S𝐀dSdS=[Az(y+dy)Az(y)]dz[Ay(z+dz)Ay(z)]dydydz=AzyAyz

The expressions for (curl𝐀)y and (curl𝐀)z are found in the same way.

Cylindrical derivation

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File:Nabla cylindrical2.svg

div𝐀=limV0V𝐀d𝐒VdV=[Aρ(ρ+dρ)(ρ+dρ)Aρ(ρ)ρ]dϕdz+[Aϕ(ϕ+dϕ)Aϕ(ϕ)]dρdz+[Az(z+dz)Az(z)]dρ(ρ+dρ/2)dϕρdϕdρdz=1ρ(ρAρ)ρ+1ρAϕϕ+Azz

(curl𝐀)ρ=limS𝝆^0S𝐀dSdS=Aϕ(z)(ρ+dρ)dϕAϕ(z+dz)(ρ+dρ)dϕ+Az(ϕ+dϕ)dzAz(ϕ)dz(ρ+dρ)dϕdz=Aϕz+1ρAzϕ

(curl𝐀)ϕ=limS𝝓^0S𝐀dSdS=Az(ρ)dzAz(ρ+dρ)dz+Aρ(z+dz)dρAρ(z)dρdρdz=Azρ+Aρz

(curl𝐀)z=limS𝒛^0S𝐀dSdS=Aρ(ϕ)dρAρ(ϕ+dϕ)dρ+Aϕ(ρ+dρ)(ρ+dρ)dϕAϕ(ρ)ρdϕρdρdϕ=1ρAρϕ+1ρ(ρAϕ)ρ

curl𝐀=(curl𝐀)ρ𝝆^+(curl𝐀)ϕ𝝓^+(curl𝐀)z𝒛^=(1ρAzϕAϕz)𝝆^+(AρzAzρ)𝝓^+1ρ((ρAϕ)ρAρϕ)𝒛^

Spherical derivation

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File:Nabla spherical2.svg div𝐀=limV0V𝐀d𝐒VdV=[Ar(r+dr)(r+dr)2Ar(r)r2]sinθdθdϕ+[Aθ(θ+dθ)sin(θ+dθ)Aθ(θ)sinθ]rdrdϕ+[Aϕ(ϕ+dϕ)Aϕ(ϕ)]rdrdθdrrdθrsinθdϕ=1r2(r2Ar)r+1rsinθ(Aθsinθ)θ+1rsinθAϕϕ

(curl𝐀)r=limS𝒓^0S𝐀dSdS=Aθ(ϕ)rdθ+Aϕ(θ+dθ)rsin(θ+dθ)dϕAθ(ϕ+dϕ)rdθAϕ(θ)rsin(θ)dϕrdθrsinθdϕ=1rsinθ(Aϕsinθ)θ1rsinθAθϕ

(curl𝐀)θ=limS𝜽^0S𝐀dSdS=Aϕ(r)rsinθdϕ+Ar(ϕ+dϕ)drAϕ(r+dr)(r+dr)sinθdϕAr(ϕ)drdrrsinθdϕ=1rsinθArϕ1r(rAϕ)r

(curl𝐀)ϕ=limS𝝓^0S𝐀dSdS=Ar(θ)dr+Aθ(r+dr)(r+dr)dθAr(θ+dθ)drAθ(r)rdθrdrdθ=1r(rAθ)r1rArθ

curl𝐀=(curl𝐀)r𝒓^+(curl𝐀)θ𝜽^+(curl𝐀)ϕ𝝓^=1rsinθ((Aϕsinθ)θAθϕ)𝒓^+1r(1sinθArϕ(rAϕ)r)𝜽^+1r((rAθ)rArθ)𝝓^

Unit vector conversion formula

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The unit vector of a coordinate parameter u is defined in such a way that a small positive change in u causes the position vector 𝐫 to change in 𝐮 direction.

Therefore, 𝐫u=su𝐮 where s is the arc length parameter.

For two sets of coordinate systems ui and vj, according to chain rule, d𝐫=i𝐫uidui=isui𝐮^idui=jsvj𝐯^jdvj=jsvj𝐯^jivjuidui=ijsvjvjui𝐯^jdui.

Now, we isolate the ith component. For ik, let duk=0. Then divide on both sides by dui to get: sui𝐮^i=jsvjvjui𝐯^j.

See also

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References

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  1. ^ a b c d e f g h Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  2. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  3. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  4. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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