Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates
Molecular-scale understanding of rheological properties of small-molecular liquids and polymers is critical to optimizing their performance in practical applications such as lubrication and hydraulic fracking. We combine nonequilibrium molecular dynamics simulations with two unsupervised machine lea...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-05-01
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| Series: | Polymers |
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| Online Access: | https://www.mdpi.com/2073-4360/15/9/2166 |
| _version_ | 1797601802785390592 |
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| author | Wenhui Li JCS Kadupitiya Vikram Jadhao |
| author_facet | Wenhui Li JCS Kadupitiya Vikram Jadhao |
| author_sort | Wenhui Li |
| collection | DOAJ |
| description | Molecular-scale understanding of rheological properties of small-molecular liquids and polymers is critical to optimizing their performance in practical applications such as lubrication and hydraulic fracking. We combine nonequilibrium molecular dynamics simulations with two unsupervised machine learning methods: principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE), to extract the correlation between the rheological properties and molecular structure of squalane sheared at high strain rates (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mn>6</mn></msup></semantics></math></inline-formula>–<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mn>10</mn></msup></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow><mi mathvariant="normal">s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula>) for which substantial shear thinning is observed under pressures <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>∈</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>–955 MPa at 293 K. Intramolecular atom pair orientation tensors of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>435</mn><mo>×</mo><mn>6</mn></mrow></semantics></math></inline-formula> dimensions and the intermolecular atom pair orientation tensors of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>61</mn><mo>×</mo><mn>6</mn></mrow></semantics></math></inline-formula> dimensions are reduced and visualized using PCA and t-SNE to assess the changes in the orientation order during the shear thinning of squalane. Dimension reduction of intramolecular orientation tensors at low pressures <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>=</mo><mn>0.1</mn><mo>,</mo><mn>100</mn></mrow></semantics></math></inline-formula> MPa reveals a strong correlation between changes in strain rate and the orientation of the side-backbone atom pairs, end-backbone atom pairs, short backbone-backbone atom pairs, and long backbone-backbone atom pairs associated with a squalane molecule. At high pressures <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>≥</mo><mn>400</mn></mrow></semantics></math></inline-formula> MPa, the orientation tensors are better classified by these different pair types rather than strain rate, signaling an overall limited evolution of intramolecular orientation with changes in strain rate. Dimension reduction also finds no clear evidence of the link between shear thinning at high pressures and changes in the intermolecular orientation. The alignment of squalane molecules is found to be saturated over the entire range of rates during which squalane exhibits substantial shear thinning at high pressures. |
| first_indexed | 2024-03-11T04:09:03Z |
| format | Article |
| id | doaj.art-57ce509d6afb4652ab9091f7c4cd78e9 |
| institution | Directory Open Access Journal |
| issn | 2073-4360 |
| language | English |
| last_indexed | 2024-03-11T04:09:03Z |
| publishDate | 2023-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Polymers |
| spelling | doaj.art-57ce509d6afb4652ab9091f7c4cd78e92023-11-17T23:36:06ZengMDPI AGPolymers2073-43602023-05-01159216610.3390/polym15092166Rheological Properties of Small-Molecular Liquids at High Shear Strain RatesWenhui Li0JCS Kadupitiya1Vikram Jadhao2Intelligent Systems Engineering, Indiana University, Bloomington, IN 47408, USAIntelligent Systems Engineering, Indiana University, Bloomington, IN 47408, USAIntelligent Systems Engineering, Indiana University, Bloomington, IN 47408, USAMolecular-scale understanding of rheological properties of small-molecular liquids and polymers is critical to optimizing their performance in practical applications such as lubrication and hydraulic fracking. We combine nonequilibrium molecular dynamics simulations with two unsupervised machine learning methods: principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE), to extract the correlation between the rheological properties and molecular structure of squalane sheared at high strain rates (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mn>6</mn></msup></semantics></math></inline-formula>–<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mn>10</mn><mn>10</mn></msup></semantics></math></inline-formula><inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mrow><mi mathvariant="normal">s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></semantics></math></inline-formula>) for which substantial shear thinning is observed under pressures <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>∈</mo><mn>0.1</mn></mrow></semantics></math></inline-formula>–955 MPa at 293 K. Intramolecular atom pair orientation tensors of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>435</mn><mo>×</mo><mn>6</mn></mrow></semantics></math></inline-formula> dimensions and the intermolecular atom pair orientation tensors of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>61</mn><mo>×</mo><mn>6</mn></mrow></semantics></math></inline-formula> dimensions are reduced and visualized using PCA and t-SNE to assess the changes in the orientation order during the shear thinning of squalane. Dimension reduction of intramolecular orientation tensors at low pressures <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>=</mo><mn>0.1</mn><mo>,</mo><mn>100</mn></mrow></semantics></math></inline-formula> MPa reveals a strong correlation between changes in strain rate and the orientation of the side-backbone atom pairs, end-backbone atom pairs, short backbone-backbone atom pairs, and long backbone-backbone atom pairs associated with a squalane molecule. At high pressures <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>P</mi><mo>≥</mo><mn>400</mn></mrow></semantics></math></inline-formula> MPa, the orientation tensors are better classified by these different pair types rather than strain rate, signaling an overall limited evolution of intramolecular orientation with changes in strain rate. Dimension reduction also finds no clear evidence of the link between shear thinning at high pressures and changes in the intermolecular orientation. The alignment of squalane molecules is found to be saturated over the entire range of rates during which squalane exhibits substantial shear thinning at high pressures.https://www.mdpi.com/2073-4360/15/9/2166shear thinningmolecular orientationnonequilibrium molecular dynamics simulationsmachine learningprincipal component analysiselastohydrodynamic lubrication |
| spellingShingle | Wenhui Li JCS Kadupitiya Vikram Jadhao Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates Polymers shear thinning molecular orientation nonequilibrium molecular dynamics simulations machine learning principal component analysis elastohydrodynamic lubrication |
| title | Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates |
| title_full | Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates |
| title_fullStr | Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates |
| title_full_unstemmed | Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates |
| title_short | Rheological Properties of Small-Molecular Liquids at High Shear Strain Rates |
| title_sort | rheological properties of small molecular liquids at high shear strain rates |
| topic | shear thinning molecular orientation nonequilibrium molecular dynamics simulations machine learning principal component analysis elastohydrodynamic lubrication |
| url | https://www.mdpi.com/2073-4360/15/9/2166 |
| work_keys_str_mv | AT wenhuili rheologicalpropertiesofsmallmolecularliquidsathighshearstrainrates AT jcskadupitiya rheologicalpropertiesofsmallmolecularliquidsathighshearstrainrates AT vikramjadhao rheologicalpropertiesofsmallmolecularliquidsathighshearstrainrates |