Three-dimensional hydrodynamic modelling in a bay of the Lake Mälaren to assess environmental impacts from a cooling and heating power plant production

The power production company Norrenergi owns a power plant in Solna, Stockholm county, Sweden, to produce heating or cooling energy by exploiting intake water’s temperature. In its current configuration, the power plant is connected to the network of the Bromma sewage treatment plant, located in the northern part of Stockholm and uses this water for production. The planned commissioning of a new sewage treatment plant in Henriksdal in the southern part of the city, thought to replace the Bromma sewage treatment plant, will lead the current sewage network used by Norrenergi’s power plant to be decommissioned. In order to maintain water supply for its power plant, Norrenergi is now seeking environmental permit to use water from the Bällstaviken bay in Solna where the old intake and outlet structures exist. This article presents the hydrodynamical modelling performed as part of the environmental permit application. The work has focused on describing the thermal dispersion conditions for an extreme energy demand in the summer (cooling production), where the released water temperature is increased between 5.5 and 10.0 °C during a daily cycle. Hydrodynamic modelling has been performed with the software TELEMAC-3D version 7.3. The first part of the modelling work has been to perform flow measurements in order to calibrate the model with respect to currents. Some preliminary dispersion tests showed that in their current configuration, the current intake and outlet structures, both located in the Bällstaviken bay, do not offer optimal production capacity due to a very high risk for a temperature shortcut. To mitigate this risk, a new location for the inlet has been investigated. A location in the adjacent Ulvsundasjön bay has been chosen which offers the possibility to take water from a greater depth with a cooler temperature especially during summer months, making it possible to reduce the relative temperature difference between the intake and outlet depths, hence lowering the environmental impacts. The thermal dispersion modelling has been performed for this intake configuration for several representative wind speeds and directions. The results show that the water temperature in the Bällstaviken bay is significantly increased due to its relatively small volume whereas impacts are, as expected, lower in the adjacent Ulvsundasjön bay which has a greater volume. The results also show a clear influence of wind direction on thermal dispersion conditions. The environmental risk assessment shows that the planned production is not expected to significantly alter the flora and fauna in the study area mainly due its current low ecological status

Overview and lessons learned from performing tailings dam breach modelling with TELEMAC-2D

Hydrodynamic

The Projected Dark and Baryonic Ellipsoidal Structure of 20 CLASH Galaxy Clusters

We reconstruct the two-dimensional (2D) matter distributions in 20 high-mass galaxy clusters selected from the CLASH survey by using the new approach of performing a joint weak gravitational lensing analysis of 2D shear and azimuthally averaged magnification measurements. This combination allows for a complete analysis of the field, effectively breaking the mass-sheet degeneracy. In a Bayesian framework, we simultaneously constrain the mass profile and morphology of each individual cluster, assuming an elliptical Navarro-Frenk-White halo characterized by the mass, concentration, projected axis ratio, and position angle (PA) of the projected major axis. We find that spherical mass estimates of the clusters from azimuthally averaged weak-lensing measurements in previous work are in excellent agreement with our results from a full 2D analysis. Combining all 20 clusters in our sample, we detect the elliptical shape of weak-lensing halos at the 5σ significance level within a scale of 2 Mpc h. The median projected axis ratio is 0.67 ± 0.07 at a virial mass of M = (15.2 ± 2.8) × 10 M, which is in agreement with theoretical predictions from recent numerical simulations of the standard collisionless cold dark matter model. We also study misalignment statistics of the brightest cluster galaxy, X-ray, thermal Sunyaev-Zel'dovich effect, and strong-lensing morphologies with respect to the weak-lensing signal. Among the three baryonic tracers studied here, we find that the X-ray morphology is best aligned with the weak-lensing mass distribution, with a median misalignment angle of |ΔPA| = 21° ± 7°. We also conduct a stacked quadrupole shear analysis of the 20 clusters assuming that the X-ray major axis is aligned with that of the projected mass distribution. This yields a consistent axis ratio of 0.67 ± 0.10, suggesting again a tight alignment between the intracluster gas and dark matter. © 2018. The American Astronomical Society. All rights reserved.This work was made possible by the availability of high-quality weak-lensing data produced by the CLASH survey. We are grateful to the CLASH team who enabled us to carry out this work. We thank the anonymous referee for constructive suggestions and comments. We thank Masamune Oguri for making his simulated Subaru Suprime-Cam observations available to us. K.U. acknowledges support from the Ministry of Science and Technology of Taiwan (grants MOST 103-2112-M-001-030-MY3 and MOST 106-2628-M-001-003-MY3) and from the Academia Sinica Investigator Award. M.S. and S.E. acknowledge financial support from the contracts ASI-INAF I/009/10/0, NARO15 ASI-INAF I/037/12/0, ASI 2015-046-R.0 and ASI-INAF n.2017-14-H.0. Support for D.G. was provided by NASA through Einstein Postdoctoral Fellowship grant number PF5-160138 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. T.O. acknowledges support from the Ministry of Science and Technology of Taiwan under the grant MOST 106-2119-M-001-031-MY3. M.M., M.S., S.E., and J.S. acknowledge support from the Italian Ministry of Foreign Affairs and International Cooperation, Directorate General for Country Promotion (Project "Crack the lens"). J.S. was supported by NSF/AST-1617022

The Projected Dark and Baryonic Ellipsoidal Structure of 20 CLASH Galaxy Clusters

We reconstruct the two-dimensional (2D) matter distributions in 20 high-mass galaxy clusters selected from the CLASH survey by using the new approach of performing a joint weak gravitational lensing analysis of 2D shear and azimuthally averaged magnification measurements. This combination allows for a complete analysis of the field, effectively breaking the mass-sheet degeneracy. In a Bayesian framework, we simultaneously constrain the mass profile and morphology of each individual cluster, assuming an elliptical Navarro–Frenk–White halo characterized by the mass, concentration, projected axis ratio, and position angle (PA) of the projected major axis. We find that spherical mass estimates of the clusters from azimuthally averaged weak-lensing measurements in previous work are in excellent agreement with our results from a full 2D analysis. Combining all 20 clusters in our sample, we detect the elliptical shape of weak-lensing halos at the 5σ significance level within a scale of 2 $\mathrm{Mpc}\,{h}^{-1}$. The median projected axis ratio is 0.67 ± 0.07 at a virial mass of ${M}_{\mathrm{vir}}=(15.2\pm 2.8)\times {10}^{14}\,{M}_{\odot }$, which is in agreement with theoretical predictions from recent numerical simulations of the standard collisionless cold dark matter model. We also study misalignment statistics of the brightest cluster galaxy, X-ray, thermal Sunyaev–Zel'dovich effect, and strong-lensing morphologies with respect to the weak-lensing signal. Among the three baryonic tracers studied here, we find that the X-ray morphology is best aligned with the weak-lensing mass distribution, with a median misalignment angle of $| {\rm{\Delta }}\mathrm{PA}| =21^\circ \pm 7^\circ$. We also conduct a stacked quadrupole shear analysis of the 20 clusters assuming that the X-ray major axis is aligned with that of the projected mass distribution. This yields a consistent axis ratio of 0.67 ± 0.10, suggesting again a tight alignment between the intracluster gas and dark matter