the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 May 2024
Modeling Inertial Deposition of Aerosol Particles in Geometrically Complicated Flow Systems Using Finite Element Methods
Abstract. This work presents a modeling approach for calculating the trajectories of aerosol particles in geometrically complicated flow systems. The finite-element based modeling is first validated by comparing the calculated inertial deposition with literature values for two cases of laminar flow: a 90-degree bend and an abrupt contraction of a pipe. The approach is then applied on a multi-part aerosol instrument used for Cantilever-Enhanced-Photo-Acoustic-Spectroscope (CEPAS) measurements. The particle transmission of the CEPAS is experimentally measured and compared to the modeling results. It is demonstrated that the model provides valuable insight on the inertial deposition losses by pinpointing their physical locations within the measurement instrument.
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Status: closed
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RC1: 'Comment on egusphere-2024-1242', Anonymous Referee #1, 12 Jun 2024
The manuscript presents a finite-element modeling approach for calculating the trajectories and inertial deposition losses of aerosol particles in flow systems. The authors validate their approach by comparing their results with literature values for two simple geometries (a 90-degree bend and an abrupt contraction) and then apply the model to a multi-part aerosol instrument used for Cantilever-Enhanced Photo-Acoustic Spectroscopy (CEPAS) measurements. The modeling results are compared to experimental measurements of particle transmission through the CEPAS.
I do not have concerns with the modeling itself. However, I think the novelty of this paper is not clear. The authors need to clearly state what is new in this paper. The modeling was done using COMSOL and its particle module, which is commercially available, and the modeling results are similar to those from empirical equations. I feel this paper is just applying commercial software to calculate a well-studied problem.
Citation: https://doi.org/10.5194/egusphere-2024-1242-RC1 -
AC1: 'Reply on RC1', Patrick Grahn, 19 Sep 2024
Thank you for taking the time to read and provide valuable feedback on our manuscript.
We understand your concern regarding the perceived lack of novelty. In response, we have revised the manuscript to improve clarity and emphasize its novelty. The main point we wish to underline, which was not clearly conveyed in the initial submission, is that the first two test cases were specifically designed to validate the COMSOL model parameterization. The primary result and novel contribution of this study is the characterization of deposition losses within the CEPAS absorption instrument—an analysis that has not been conducted previously.
CEPAS is a relatively new and highly sensitive aerosol instrument, with measurement capabilities an order of magnitude higher than other available absorption measurement instruments. Therefore, we believe its significance to the field, as well as the importance of this paper, will grow as its use becomes more widespread.
Citation: https://doi.org/10.5194/egusphere-2024-1242-AC1
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AC1: 'Reply on RC1', Patrick Grahn, 19 Sep 2024
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RC2: 'Comment on egusphere-2024-1242', Anonymous Referee #2, 22 Jul 2024
This manuscript used finite element methods to simulate particle deposition in two cases of laminar flow and a third case of a multi-part aerosol instrument. The simulation results of the first two cases were comparable to empirical equations. The simulation results of the third case had an offset compared to the experimental results and showed where the particles deposited.
The reviewer does not see much novelty in modeling the first two cases because the methods for them are mature. There might be novelty in modeling the multi-part aerosol instrument, but the introduction section does not emphasize enough the need for this research. The authors identified and explained the offset between the model and experimental results (the under pressure of the particle counter pump) in the third case, but no action was taken to resolve this issue. The authors mentioned that removing tube fittings improved particle transmission as a contribution of the modeling work without presenting this in the manuscript, making the importance not quite clear.
Citation: https://doi.org/10.5194/egusphere-2024-1242-RC2 -
AC2: 'Reply on RC2', Patrick Grahn, 19 Sep 2024
Thank you for your thoughtful review and constructive comments on our manuscript. We acknowledge the points raised and have addressed them as follows:
- Lack of novelty in the first two cases: We understand that the modeling methods applied to the first two test cases may appear well-established and not novel. We want to emphasize that the primary goal of these test cases was not to explore new methods but to validate our COMSOL model against known empirical equations. We have revised the introduction to better clarify this objective and to explain why this validation is important for ensuring the reliability of the more complex third case, which forms the core of our study.
- Emphasizing the need for research in the third case: We agree that the introduction did not sufficiently highlight the need for the modeling work on the multi-part aerosol instrument. We have revised the introduction to better articulate the significance of characterizing particle deposition in this instrument. Specifically, we have emphasized the implications for accurate light absorption measurements and why understanding deposition losses in the instrument is essential for improving measurement accuracy.
- Offset between model and experimental results: We recognize that no direct action was taken to resolve the offset between the model and experimental results in the third case. However, we did identify the potential source of the discrepancy (under pressure in the particle counter pump) and acknowledged this limitation in our model. We did not attempt to fully resolve the issue as we believe there is no clear way of resolving it; the CEPAS acoustic chamber cell and its inlet and outlet ports, which cause the under pressure, would need to be re-designed and re-manufactured. This is something that cannot be done within the confines of this study. We have revised the manuscript to clarify this point.
- Improvement of particle transmission by removing tube fittings: While we mentioned this as an outcome of the modeling work, we agree that it was not adequately presented in the manuscript. In response, we have removed this statement from the Conclusions section.
We hope these revisions improve the clarity of the manuscript and better communicate the novelty and contributions of our work.
Citation: https://doi.org/10.5194/egusphere-2024-1242-AC2
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AC2: 'Reply on RC2', Patrick Grahn, 19 Sep 2024
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RC3: 'Comment on egusphere-2024-1242', Anonymous Referee #3, 10 Aug 2024
The authors present finite-element modeling of a few aerosol sampling ducts, including a 90-degree bend, a contracted pipe, and a Cantilever-Enhanced-Photo-Acoustic-Spectroscope (CEPAS). The particle tracing module is used to evaluate the aerosol transmission efficiency. The authors demonstrated the finite-element based modeling is capable of simulating particle losses and pinpointing their physical locations in the CEPAS.
Identifying particle losses is a well-studied engineering problem, and finite-element modeling using commercially available software is a common practice in this field. Therefore, this manuscript does not appear to offer new insights or significant advancements in measuring techniques. Nevertheless, I would encourage the authors to look into the discrepancy between model simulation and experimental characterization on the CEPAS, to make this a well-performed work. Â
Citation: https://doi.org/10.5194/egusphere-2024-1242-RC3 -
AC3: 'Reply on RC3', Patrick Grahn, 19 Sep 2024
Thank you for your thoughtful comments and for taking the time to review our manuscript.
We acknowledge your point that identifying particle losses is a well-studied problem and that finite-element modeling using commercially available software is used in this field. In response, we have worked to clarify the novelty and purpose of our study, specifically underlining the characterization of deposition losses within the CEPAS. This is an underexplored area in aerosol research, as previous studies have not quantitatively evaluated particle transmission losses within this instrument.
We appreciate your suggestion to focus on resolving the discrepancy between model simulation and experimental results. We have taken steps to further investigate this issue. As mentioned in the original submission, we identified that under pressure in the particle counter pump contributed to this offset. In the revised manuscript, we have acknowledged the difficulty in resolving this issue and, in addition, stated that the CEPAS could be redesigned to allow for better control of pressure levels. While the experimental setup did limit our ability to take immediate action to correct the under-pressure issue, we believe our findings still offer valuable insights into how CEPAS can be optimized for future studies.
Citation: https://doi.org/10.5194/egusphere-2024-1242-AC3
-
AC3: 'Reply on RC3', Patrick Grahn, 19 Sep 2024
Status: closed
-
RC1: 'Comment on egusphere-2024-1242', Anonymous Referee #1, 12 Jun 2024
The manuscript presents a finite-element modeling approach for calculating the trajectories and inertial deposition losses of aerosol particles in flow systems. The authors validate their approach by comparing their results with literature values for two simple geometries (a 90-degree bend and an abrupt contraction) and then apply the model to a multi-part aerosol instrument used for Cantilever-Enhanced Photo-Acoustic Spectroscopy (CEPAS) measurements. The modeling results are compared to experimental measurements of particle transmission through the CEPAS.
I do not have concerns with the modeling itself. However, I think the novelty of this paper is not clear. The authors need to clearly state what is new in this paper. The modeling was done using COMSOL and its particle module, which is commercially available, and the modeling results are similar to those from empirical equations. I feel this paper is just applying commercial software to calculate a well-studied problem.
Citation: https://doi.org/10.5194/egusphere-2024-1242-RC1 -
AC1: 'Reply on RC1', Patrick Grahn, 19 Sep 2024
Thank you for taking the time to read and provide valuable feedback on our manuscript.
We understand your concern regarding the perceived lack of novelty. In response, we have revised the manuscript to improve clarity and emphasize its novelty. The main point we wish to underline, which was not clearly conveyed in the initial submission, is that the first two test cases were specifically designed to validate the COMSOL model parameterization. The primary result and novel contribution of this study is the characterization of deposition losses within the CEPAS absorption instrument—an analysis that has not been conducted previously.
CEPAS is a relatively new and highly sensitive aerosol instrument, with measurement capabilities an order of magnitude higher than other available absorption measurement instruments. Therefore, we believe its significance to the field, as well as the importance of this paper, will grow as its use becomes more widespread.
Citation: https://doi.org/10.5194/egusphere-2024-1242-AC1
-
AC1: 'Reply on RC1', Patrick Grahn, 19 Sep 2024
-
RC2: 'Comment on egusphere-2024-1242', Anonymous Referee #2, 22 Jul 2024
This manuscript used finite element methods to simulate particle deposition in two cases of laminar flow and a third case of a multi-part aerosol instrument. The simulation results of the first two cases were comparable to empirical equations. The simulation results of the third case had an offset compared to the experimental results and showed where the particles deposited.
The reviewer does not see much novelty in modeling the first two cases because the methods for them are mature. There might be novelty in modeling the multi-part aerosol instrument, but the introduction section does not emphasize enough the need for this research. The authors identified and explained the offset between the model and experimental results (the under pressure of the particle counter pump) in the third case, but no action was taken to resolve this issue. The authors mentioned that removing tube fittings improved particle transmission as a contribution of the modeling work without presenting this in the manuscript, making the importance not quite clear.
Citation: https://doi.org/10.5194/egusphere-2024-1242-RC2 -
AC2: 'Reply on RC2', Patrick Grahn, 19 Sep 2024
Thank you for your thoughtful review and constructive comments on our manuscript. We acknowledge the points raised and have addressed them as follows:
- Lack of novelty in the first two cases: We understand that the modeling methods applied to the first two test cases may appear well-established and not novel. We want to emphasize that the primary goal of these test cases was not to explore new methods but to validate our COMSOL model against known empirical equations. We have revised the introduction to better clarify this objective and to explain why this validation is important for ensuring the reliability of the more complex third case, which forms the core of our study.
- Emphasizing the need for research in the third case: We agree that the introduction did not sufficiently highlight the need for the modeling work on the multi-part aerosol instrument. We have revised the introduction to better articulate the significance of characterizing particle deposition in this instrument. Specifically, we have emphasized the implications for accurate light absorption measurements and why understanding deposition losses in the instrument is essential for improving measurement accuracy.
- Offset between model and experimental results: We recognize that no direct action was taken to resolve the offset between the model and experimental results in the third case. However, we did identify the potential source of the discrepancy (under pressure in the particle counter pump) and acknowledged this limitation in our model. We did not attempt to fully resolve the issue as we believe there is no clear way of resolving it; the CEPAS acoustic chamber cell and its inlet and outlet ports, which cause the under pressure, would need to be re-designed and re-manufactured. This is something that cannot be done within the confines of this study. We have revised the manuscript to clarify this point.
- Improvement of particle transmission by removing tube fittings: While we mentioned this as an outcome of the modeling work, we agree that it was not adequately presented in the manuscript. In response, we have removed this statement from the Conclusions section.
We hope these revisions improve the clarity of the manuscript and better communicate the novelty and contributions of our work.
Citation: https://doi.org/10.5194/egusphere-2024-1242-AC2
-
AC2: 'Reply on RC2', Patrick Grahn, 19 Sep 2024
-
RC3: 'Comment on egusphere-2024-1242', Anonymous Referee #3, 10 Aug 2024
The authors present finite-element modeling of a few aerosol sampling ducts, including a 90-degree bend, a contracted pipe, and a Cantilever-Enhanced-Photo-Acoustic-Spectroscope (CEPAS). The particle tracing module is used to evaluate the aerosol transmission efficiency. The authors demonstrated the finite-element based modeling is capable of simulating particle losses and pinpointing their physical locations in the CEPAS.
Identifying particle losses is a well-studied engineering problem, and finite-element modeling using commercially available software is a common practice in this field. Therefore, this manuscript does not appear to offer new insights or significant advancements in measuring techniques. Nevertheless, I would encourage the authors to look into the discrepancy between model simulation and experimental characterization on the CEPAS, to make this a well-performed work. Â
Citation: https://doi.org/10.5194/egusphere-2024-1242-RC3 -
AC3: 'Reply on RC3', Patrick Grahn, 19 Sep 2024
Thank you for your thoughtful comments and for taking the time to review our manuscript.
We acknowledge your point that identifying particle losses is a well-studied problem and that finite-element modeling using commercially available software is used in this field. In response, we have worked to clarify the novelty and purpose of our study, specifically underlining the characterization of deposition losses within the CEPAS. This is an underexplored area in aerosol research, as previous studies have not quantitatively evaluated particle transmission losses within this instrument.
We appreciate your suggestion to focus on resolving the discrepancy between model simulation and experimental results. We have taken steps to further investigate this issue. As mentioned in the original submission, we identified that under pressure in the particle counter pump contributed to this offset. In the revised manuscript, we have acknowledged the difficulty in resolving this issue and, in addition, stated that the CEPAS could be redesigned to allow for better control of pressure levels. While the experimental setup did limit our ability to take immediate action to correct the under-pressure issue, we believe our findings still offer valuable insights into how CEPAS can be optimized for future studies.
Citation: https://doi.org/10.5194/egusphere-2024-1242-AC3
-
AC3: 'Reply on RC3', Patrick Grahn, 19 Sep 2024
Model code and software
COMSOL models for inertial deposition of particles in laminar flow Patrick Grahn https://doi.org/10.5281/zenodo.11003261
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