1. EXT1 - External wrapping This component can be used to model additional weight or buoyancy modules attached to a riser line. The specified additional weight and buoyancy are used to adjust the average properties of the segment. 1.1. Data group identifier NEW COMPonent EXT1 1.2. Component type identifier CMPTYP-ID CMPTYP-ID: character(8): Component type identifier 1.3. Mass and volume AMS AE RGYR FRAC AMS: real: Mass per unit length \(\mathrm {[M/L]}\) AE: real: Buoyancy volume/length \(\mathrm {[L^2]}\) RGYR: real: Radius of gyration around local x-axis \(\mathrm {[L]}\) FRAC: real: Fraction of the segment that is covered \(\mathrm {[1]}\) 0 <= FRAC <= 1 The resulting properties of the segment with external wrapping are: Mass / length: \(\mathrm {AMS_{res}=AMS_{cs}+AMS_{ext}\times FRAC}\) Resulting radius of gyration: \(\mathrm {RGYR_{res}=(AMS_{cs}\times RGYR_{cs}^2+AMS_{ext}\times RGYR_{ext}^2\times FRAC)/(AMS_{cs}+AMS_{ext}\times FRAC)}\) Resulting external area for buoyancy: \(\mathrm {AE_{res}=AE_{cs}+AE_{ext}\times FRAC}\) Where: cs denotes the original cross section properties; i.e. without wrapping. ext denotes the properties of the wrapping given in this data group. res denotes the resulting average segment properties Figure 1. Description of external wrapping 1.4. Hydrodynamic coefficients CDX CDY AMX AMY CDLX CDLY CDX: real: Drag force coefficient in tangential direction \(\mathrm {[F/((L/T)^2\times L)]}\) CDY: real: Drag force coefficient in normal direction \(\mathrm {[F/((L/T)^2\times L)]}\) AMX: real: Added mass per length in tangential direction \(\mathrm {[M/L]}\) AMY: real: Added mass per length in normal direction \(\mathrm {[M/L]}\) CDLX: real, default: 0: Linear drag force coefficients in tangential direction \(\mathrm {[F/((L/T)\times L)]}\) CDLY: real, default: 0: Linear drag force coefficients in normal direction \(\mathrm {[F/((L/T)\times L)]}\) The coefficients specified for the external wrapping are added directly to the coefficients specified for the pipe. The drag forces per unit length acting in the local x-direction is computed as: \(\mathrm {F_x=(CDX_R+FRAC\times CDX)VRELX\times VRELX+(CDLX_R+FRAC\times CDLX)VRELX}\) In the case of an axis symmetric cross section the drag force per unit length, \(\mathrm {F_n}\), acting normal to the local x-axis is computed by assuming that the instantaneous drag force direction is parallel to the instantaneous transverse relative velocity component \(\begin{array}{l}\mathrm {F_n=(CDY_R+FRAC\times CDY)(VRELY^2+VRELZ^2)}\\+\mathrm {(CDLY_R+FRAC\times CDLY)\sqrt{VRELY^2+VREZ^2}}\end{array}\) In the case of a cross section with 2 symmetry planes the drag force per unit length in the local y and z directions are computed as: \(\mathrm {F_y=(CDY_R+FRAC\times CDY)VRELY\times VRELY+(CDLY_R+FRAC\times CDLY)VRELY}\) \(\mathrm {F_z=(CDZ_R+FRAC\times CDZ)VRELZ\times VRELZ+(CDLZ_R+FRAC\times CDLZ)VRELZ}\) Where: \(\mathrm {CDX_R,CDY_R,CDZ_R}\): are the input quadratic drag force coefficients of the riser in local x,y and z-directions \(\mathrm {CDLX_R,CDLY_R,CDLZ_R}\): are the input linear drag force coefficient of the riser in local x,y and z-directions \(\mathrm {CDX,CDY}\): are the input quadratic drag force coefficients of the external wrapping in local x and y-directions \(\mathrm {CDLX,CDLY}\): are the input linear drag force coefficients of the external wrapping in local x andy-directions \(\mathrm {VRELX,VRELY,VRELZ}\): are relative water velocities in local x, y and z-directions For an axis symmetric pipe with external wrapping the input drag force coefficient in normal direction can be calculated as: \(\mathrm {CDY=\frac{1}{2}\rho (DC_{dn}-D_RC_{dnR})}\) The added mass per unit length in normal direction can be calculated as: \(\mathrm {AMY=\rho \frac{\pi }{4}(D^2C_{mn}-D_R^2C_{mnR})}\) where: \(\mathrm {\rho }\): water density \(\mathrm {D}\): outer diameter of the external wrapping \(\mathrm {D_R}\): outer diameter of the pipe \(\mathrm {C_{dn}}\): normal drag coefficient \(\mathrm {C_{dnR}}\): normal drag coefficient of the pipe \(\mathrm {C_{mn}}\): normal added mass coefficient of the external wrapping \(\mathrm {C_{mnR}}\): normal added mass coefficient of the pipe Marine growth Environmental Data