Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions
| dc.contributor.author | Khan, Idrees | |
| dc.contributor.author | Chinyoka, Tiri | |
| dc.contributor.author | Gill, Andrew | |
| dc.date.accessioned | 2022-04-11T11:36:37Z | |
| dc.date.available | 2022-04-11T11:36:37Z | |
| dc.date.issued | 2022-02-25 | |
| dc.date.updated | 2022-03-10T14:18:33Z | |
| dc.description.abstract | We investigated the shear banding phenomena in the non-isothermal simple-shear flow of a viscoelastic-fluid-based nanofluid (VFBN) subject to exothermic reactions. The polymeric (viscoelastic) behavior of the VFBN was modeled via the Giesekus constitutive equation, with appropriate adjustments to incorporate both the non-isothermal and nanoparticle effects. Nahme-type laws were employed to describe the temperature dependence of the VFBN viscosities and relaxation times. The Arrhenius theory was used for the modeling and incorporation of exothermic reactions. The VFBN was modeled as a single-phase homogeneous-mixture and, hence, the effects of the nanoparticles were based on the volume fraction parameter. Efficient numerical schemes based on semi-implicit finite-difference-methods were employed in MATLAB for the computational solution of the governing systems of partial differential equations. The fundamental fluid-dynamical and thermodynamical phenomena, such as shear banding, thermal runaway, and heat transfer rate (HTR) enhancement, were explored under relevant conditions. Important novel results of industrial significance were observed and demonstrated. Firstly, under shear banding conditions of the Giesekus-type VFBN model, we observed remarkable HTR and Therm-C enhancement in the VFBN as compared to, say, NFBN. Specifically, the results demonstrate that the VFBN are less susceptible to thermal runaway than are NFBN. Additionally, the results illustrate that the reduced susceptibility of the Giesekus-type VFBN to the thermal runaway phenomena is further enhanced under shear banding conditions, in particular when the nanofluid becomes increasingly polymeric. Increased polymer viscosity is used as the most direct proxy for measuring the increase in the polymeric nature of the fluid. | |
| dc.identifier | doi: 10.3390/en15051719 | |
| dc.identifier.apacitation | Khan, I., Chinyoka, T., & Gill, A. (2022). Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions. <i>Energies</i>, 15(5), http://hdl.handle.net/11427/36330 | en_ZA |
| dc.identifier.chicagocitation | Khan, Idrees, Tiri Chinyoka, and Andrew Gill "Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions." <i>Energies</i> 15, 5. (2022) http://hdl.handle.net/11427/36330 | en_ZA |
| dc.identifier.citation | Khan, I., Chinyoka, T. & Gill, A. 2022. Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions. <i>Energies.</i> 15(5) http://hdl.handle.net/11427/36330 | en_ZA |
| dc.identifier.ris | TY - Journal Article AU - Khan, Idrees AU - Chinyoka, Tiri AU - Gill, Andrew AB - We investigated the shear banding phenomena in the non-isothermal simple-shear flow of a viscoelastic-fluid-based nanofluid (VFBN) subject to exothermic reactions. The polymeric (viscoelastic) behavior of the VFBN was modeled via the Giesekus constitutive equation, with appropriate adjustments to incorporate both the non-isothermal and nanoparticle effects. Nahme-type laws were employed to describe the temperature dependence of the VFBN viscosities and relaxation times. The Arrhenius theory was used for the modeling and incorporation of exothermic reactions. The VFBN was modeled as a single-phase homogeneous-mixture and, hence, the effects of the nanoparticles were based on the volume fraction parameter. Efficient numerical schemes based on semi-implicit finite-difference-methods were employed in MATLAB for the computational solution of the governing systems of partial differential equations. The fundamental fluid-dynamical and thermodynamical phenomena, such as shear banding, thermal runaway, and heat transfer rate (HTR) enhancement, were explored under relevant conditions. Important novel results of industrial significance were observed and demonstrated. Firstly, under shear banding conditions of the Giesekus-type VFBN model, we observed remarkable HTR and Therm-C enhancement in the VFBN as compared to, say, NFBN. Specifically, the results demonstrate that the VFBN are less susceptible to thermal runaway than are NFBN. Additionally, the results illustrate that the reduced susceptibility of the Giesekus-type VFBN to the thermal runaway phenomena is further enhanced under shear banding conditions, in particular when the nanofluid becomes increasingly polymeric. Increased polymer viscosity is used as the most direct proxy for measuring the increase in the polymeric nature of the fluid. DA - 2022-02-25 DB - OpenUCT DP - University of Cape Town IS - 5 J1 - Energies KW - finite-difference-methods KW - viscoelastic-fluid-based nanofluid (VFBN) KW - non-isothermal viscoelastic fluid flow KW - Giesekus model KW - nanofluid variable-thermal conductivity KW - shear banding KW - thermal-runway LK - https://open.uct.ac.za PY - 2022 T1 - Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions TI - Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions UR - http://hdl.handle.net/11427/36330 ER - | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11427/36330 | |
| dc.identifier.uri | https://doi.org/10.3390/en15051719 | |
| dc.identifier.vancouvercitation | Khan I, Chinyoka T, Gill A. Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions. Energies. 2022;15(5) http://hdl.handle.net/11427/36330. | en_ZA |
| dc.publisher | Multidisciplinary Digital Publishing Institute | |
| dc.rights.license | https://creativecommons.org/licenses/by/4.0/ | |
| dc.rights.uri | http://creativecommons.org/licenses/by/4.0/ | |
| dc.source | Energies | |
| dc.source.journalissue | 5 | |
| dc.source.journalvolume | 15 | |
| dc.source.uri | https://www.mdpi.com/journal/energies | |
| dc.subject | finite-difference-methods | |
| dc.subject | viscoelastic-fluid-based nanofluid (VFBN) | |
| dc.subject | non-isothermal viscoelastic fluid flow | |
| dc.subject | Giesekus model | |
| dc.subject | nanofluid variable-thermal conductivity | |
| dc.subject | shear banding | |
| dc.subject | thermal-runway | |
| dc.title | Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions | |
| dc.type | Journal Article |