Resilience: Accounting for the Noncomputable

Plans to solve complex environmental problems should always consider the role of surprise. Nevertheless, there is a tendency to emphasize known computable aspects of a problem while neglecting aspects that are unknown and failing to ask questions about them. The tendency to ignore the noncomputable can be countered by considering a wide range of perspectives, encouraging transparency with regard to conflicting viewpoints, stimulating a diversity of models, and managing for the emergence of new syntheses that reorganize fragmentary knowledg

Influence of the secondary motions on pollutant mixing in a meandering open channel flow

[EN] This paper presents large eddy simulation of turbulent flow in a meandering open channel with smooth wall and rectangular cross-section. The Reynolds number based on the channel height is 40,000 and the aspect ratio of the cross-section is 4.48. The depthaveraged mean stream-wise velocity agree well to experimental measurements. In this specific case, two interacting cells are formed that swap from one bend to the other. Transport and mixing of a pollutant is analysed using three different positions of release, e.g. on the inner bank, on the outer bank and on the centre of the cross section. The obtained depth-average mean concentration profiles are reasonably consistent with available experimental data. The role of the secondary motions in the mixing processes is the main focus of the discussion. It is found that the mixing when the scalar is released on the centre of the cross-section is stronger and faster than the mixing of the scalar released on the sides. When the position of release is close to a bank side, the mixing is weaker and a clear concentration of scalar close to the corresponding side-wall can be observed in both cases.MGV acknowledges the financial support of the Spanish Ministry of Education through the program Jose Castillejo.Moncho Esteve, IJ.; Folke, F.; García-Villalba, M.; Palau-Salvador, G. (2017). Influence of the secondary motions on pollutant mixing in a meandering open channel flow. Environmental Fluid Mechanics. 17(4):695-714. https://doi.org/10.1007/s10652-017-9513-4S695714174Julien PY, Duan JG (2005) Numerical simulation of the inception of channel meandering. Earth Surf Process Landf J Br Geomorphol Res Group 30:1093–1110Boussinesq J (1868) Mémoire sur l’influence des frottements dans les mouvements reguliers des fluids. J Math Pures Appl 13:377–424Thomson J (1876) On the origin of windings of rivers in alluvial plains, with remarks on the flow of water round bends in pipes. Proc R Soc Lond 25:5–8Booij R, Tukker J (1996) 3-Dimensional laser-doppler measurements in a curved flume. In: Adrian RJ, Durão DFG, Durst F, Heitor MV, Maeda M, Whitelaw JH (eds) Developments in laser techniques and applications to fluid mechanics. Springer, Berlin, pp 98–114Muto Y (1997) Turbulent flow in two-stage meandering channels. Ph.D. The University of BradfordShiono K, Muto Y (1998) Complex flow mechanisms in compound meandering channels with overbank flow. J Fluid Mech 376:221–261. doi: 10.1017/S0022112098002869Tominaga A, Nagao M, Nezu I (1999) Flow structure and momentum transport processes in curved open-channels with vegetation. In: Proceedings of 28th IAHR CongressBooij R (2003) Measurements and large eddy simulations of the flows in some curved flumes. J Turbul 4:N8. doi: 10.1088/1468-5248/4/1/008Jia Y, Blanckaert K, Wang SS (2001) Numerical simulation of secondary currents in curved channels. In: Proceedings of 8th FMTM-CongressMockmore C (1943) Flow around bends in stable channels. Trans ASCE 3:334Blanckaert K, De Vriend HJ (2004) Secondary flow in sharp open-channel bends. J Fluid Mech 498:353–380. doi: 10.1017/S0022112003006979Balen WV, Uijttewaal WSJ, Blanckaert K (2009) Large-eddy simulation of a mildly curved open-channel flow. J Fluid Mech 630:413–442. doi: 10.1017/S0022112009007277van Balen W, Blanckaert K, Uijttewaal WSJ (2010) Analysis of the role of turbulence in curved open-channel flow at different water depths by means of experiments, LES and RANS. J Turbul 11:N12. doi: 10.1080/14685241003789404Christensen HB (1999) Secondary turbulent flow in an infinte bend. Iahr Symp. River Coast. Estuar. MorphodynamicsBlanckaert K, Graf WH (2004) Momentum transport in sharp open-channel bends. J Hydraul Eng 130:186–198. doi: 10.1061/(ASCE)0733-9429(2004)130:3(186)Stoesser T, Ruether N, Olsen NRB (2010) Calculation of primary and secondary flow and boundary shear stresses in a meandering channel. Adv Water Resour 33:158–170. doi: 10.1016/j.advwatres.2009.11.001Blanckaert K, Duarte A, Chen Q, Schleiss AJ (2012) Flow processes near smooth and rough (concave) outer banks in curved open channels. J Geophys Res Earth Surf 117:F04020. doi: 10.1029/2012JF002414Vaghefi M, Akbari M, Fiouz AR (2016) An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: secondary flow and bed shear stress. KSCE J Civ Eng 20:1582–1593. doi: 10.1007/s12205-015-1560-0Kang S, Lightbody A, Hill C, Sotiropoulos F (2011) High-resolution numerical simulation of turbulence in natural waterways. Adv Water Resour 34:98–113. doi: 10.1016/j.advwatres.2010.09.018Engel FL, Rhoads BL (2016) Three-dimensional flow structure and patterns of bed shear stress in an evolving compound meander bend. Earth Surf Process Landf 41:1211–1226. doi: 10.1002/esp.3895Khosronejad A, Hansen AT, Kozarek JL, Guentzel K, Hondzo M, Guala M, Wilcock P, Finlay JC, Sotiropoulos F (2016) Large eddy simulation of turbulence and solute transport in a forested headwater stream. J Geophys Res Earth Surf 121:2014JF003423. doi: 10.1002/2014JF003423Mera I, Franca MJ, Anta J, Peña E (2015) Turbulence anisotropy in a compound meandering channel with different submergence conditions. Adv Water Resour 81:142–151. doi: 10.1016/j.advwatres.2014.10.012Termini D (2015) Momentum transport and bed shear stress distribution in a meandering bend: experimental analysis in a laboratory flume. Adv Water Resour 81:128–141. doi: 10.1016/j.advwatres.2015.01.005Chang Y (1971) Lateral mixing in meandering channels. Ph.D., The University of IowaFischer HB (1969) The effect of bends on dispersion in streams. Water Resour Res 5:496–506. doi: 10.1029/WR005i002p00496Rozovskii IL (1957) Flow of water in bends of open channels. Kiev Acad. Sci. Ukr. SSR Isr. Program Sci. Transl. Wash. DC Available Off. Tech. Serv. US Dept Commer. 1957 Ie Jerus. 1961Taylor G (1954) The dispersion of matter in turbulent flow through a pipe. Proc R Soc Lond Math Phys Eng Sci 223:446–468. doi: 10.1098/rspa.1954.0130Elder JW (1959) The dispersion of marked fluid in turbulent shear flow. J Fluid Mech 5:544–560. doi: 10.1017/S0022112059000374Boxall JB, Guymer I (2003) Analysis and prediction of transverse mixing coefficients in natural channels. J Hydraul Eng 129:129–139. doi: 10.1061/(ASCE)0733-9429(2003)129:2(129)Demuren AO, Rodi W (1984) Calculation of turbulence-driven secondary motion in non-circular ducts. J Fluid Mech 140:189–222. doi: 10.1017/S0022112084000574Sharma H, Ahmad Z (2014) Transverse mixing of pollutants in streams: a review. Can J Civ Eng 41:472–482. doi: 10.1139/cjce-2013-0561Booij R (1995) Eddy laser Doppler measurements and turbulence modeling of the flow in a curved flume. In: Proceedings of 1995 ASMEJSME Fluid Eng 6 Th Int Laser Anemometry Conference on Laser Anemometry Hilton Head SCStoesser T, Ruether N, Olsen N (2008) Near-bed flow behavior in a meandering channel. In: RiverFlow 2008 4th International Conference on Fluvial HydraulicsKang S, Sotiropoulos F (2011) Flow phenomena and mechanisms in a field-scale experimental meandering channel with a pool-riffle sequence: insights gained via numerical simulation. J Geophys Res Earth Surf 116:F03011. doi: 10.1029/2010JF001814Xu D, Bai Y, Munjiza A, Avital E, Williams J (2013) Investigation on the characteristics of turbulent flow in a meandering open channel bend using large eddy simulation. In: Proceedings of 2013 IAHR World CongressDemuren AO, Rodi W (1986) Calculation of flow and pollutant dispersion in meandering channels. J Fluid Mech 172:63–92. doi: 10.1017/S0022112086001659Breuer M, Rodi W (1994) Large-eddy simulation of turbulent flow through a straight square duct and a 180° bend. In: Voke PR, Kleiser L, Chollet J-P (eds) Direct large-eddy simulation I. Springer, Netherlands, pp 273–285Hinterberger C (2004) Dreidimensionale und tiefengemittelte large-eddy-simulation von Flachwasserströmungen. Ph.D., University of KarlsruheRhie CM, Chow WL (1983) Numerical study of the turbulent flow past an airfoil with trailing edge separation. AIAA J 21:1525–1532. doi: 10.2514/3.8284Stone H (1968) Iterative solution of implicit approximations of multidimensional partial differential equations. SIAM J Numer Anal 5:530–558. doi: 10.1137/0705044Smagorinsky J (1963) General circulation experiments with the primitive equations. Mon Weather Rev 91:99–164. doi: 10.1175/1520-0493(1963)0912.3.CO;2Hinterberger C, Fröhlich J, Rodi W (2007) Three-dimensional and depth-averaged large-eddy simulations of some shallow water flows. J Hydraul Eng. doi: 10.1061/(ASCE)0733-9429(2007)133:8(857)Zhu J (1991) A low-diffusive and oscillation-free convection scheme. Commun Appl Numer Methods 7:225–232. doi: 10.1002/cnm.1630070307Denev JA, Fröhlich J, Bockhorn H (2009) Large eddy simulation of a swirling transverse jet into a crossflow with investigation of scalar transport. Phys Fluids 21:015101. doi: 10.1063/1.3054148Palau-Salvador G, García-Villalba M, Rodi W (2011) Scalar transport from point sources in the flow around a finite-height cylinder. Environ Fluid Mech 11:611–625. doi: 10.1007/s10652-010-9199-3Fröhlich J, García-Villalba M, Rodi W (2007) Scalar mixing and large-scale coherent structures in a turbulent swirling jet. Flow Turbul Combust 80:47–59. doi: 10.1007/s10494-007-9121-3García-Villalba M, Palau-Salvador G, Rodi W (2014) Forced convection heat transfer from a finite-height cylinder. Flow Turbul Combust 93:171–187. doi: 10.1007/s10494-014-9543-7Blanckaert K, Graf WH (2001) Mean flow and turbulence in open-channel bend. J Hydraul Eng 127:835–847. doi: 10.1061/(ASCE)0733-9429(2001)127:10(835

Promoter effect on the reduction behavior of wuestite-based catalysts for ammonia synthesis

Ammonia synthesis remains one of the most important catalytic processes since it enables efficient hydrogen storage and provides the basis for the production of fertilizers. Herein, complementary bulk and local analytical techniques were combined to investigate the effect of selected promoters (Al, K, Ca) on the reduction of wuestite into α-iron and their catalytic performance for ammonia synthesis. The use of promoters appears to have a positive effect on the wuestite-derived catalyst in ammonia synthesis. The promoters seemingly act as a binder for wuestite grains and impede the reduction and disproportionation events of wuestite precursors resulting in an increased catalytic performance. This effect is associated with an increase of surface area and mesoporosity. The study delivers new insights into the interplay of structure and promoters in wuestite-based catalysts

The Dynamics of Ecosystems, Biodiversity Management and Social Institutions at High Northern Latitudes

Ecosystems at high latitudes are highly dynamic, influenced by a multitude of large-scale disturbances. Due to global change processes these systems may be expected to be particularly vulnerable, affecting the sustained production of renewable wood resources and abundance of plants and animals on which local cultures depend. In this paper, we assess the implications of new understandings of high northern latitude ecosystems and what must be done to manage systems for resilience. We suggest that the focus of land management should shift from recovery from local disturbance to sustaining ecosystem functions in the face of change and disruption. The role of biodiversity as insurance for allowing a system to reorganize and develop during the disturbance and reorganization phases needs to be addressed in management and policy. We emphasize that the current concepts of ecological reserves and protected areas need to be reconsidered to developp dynamic tools for sustainable management of ecosystems in face of change. Characteristics of what may be considered as customary reserves at high latitudes are often consistent with a more dynamic view of reserves. We suggest new directions for addressing biodiversity management in dynamic landscapes at high latitudes, and provide empirical examples of insights from unconventional perspectives that may help improve the potential for sustainable management of biodiversity and the generation of ecosystem services

Regeneration potential of the Baltic Sea inferred from historical records

Overfishing of large predatory fish populations has resulted in lasting restructurings of entire marine food webs worldwide, with potential immense socio-economic consequences. Fortunately, some degraded ecosystems have started to show signs of regeneration. A key challenge for resource management is to anticipate the degree to which regeneration is possible, given the multiple threats ecosystems face. Here, we show that under current hydroclimatic conditions, complete regeneration of a heavily altered ecosystem –the Baltic Sea as case study– would not be possible. Instead, as the ecosystem regenerates it moves towards a new ecological baseline. This new baseline is characterized by lower and more variable biomass of the commercially important Atlantic cod, even under very low exploitation rates. Consequently, societal costs increase due to higher risk premium caused by increased uncertainty in biomass and reduced consumer surplus. Specifically, the combined economic losses amount to about 120 million € per year, which equals half of today’s maximum economic yield for the Baltic cod fishery. Our analyses suggest that shifts in ecological and economic baselines, in combination with increased biomass variability, lead to higher economic uncertainty and costs for exploited ecosystems, in particular under climate change.Kiel Cluster of Excellence 'Future Ocean

Profibrotic epithelial phenotype:a central role for MRTF and TAZ

Abstract Epithelial injury is a key initiator of fibrosis but - in contrast to the previous paradigm - the epithelium in situ does not undergo wide-spread epithelial-mesenchymal/myofibroblast transition (EMT/EMyT). Instead, it assumes a Profibrotic Epithelial Phenotype (PEP) characterized by fibrogenic cytokine production. The transcriptional mechanisms underlying PEP are undefined. As we have shown that two RhoA/cytoskeleton-regulated transcriptional coactivators, Myocardin-related transcription factor (MRTF) and TAZ, are indispensable for EMyT, we asked if they might mediate PEP as well. Here we show that mechanical stress (cyclic stretch) increased the expression of transforming growth factor-β1 (TGFβ1), connective tissue growth factor (CTGF), platelet-derived growth factor and Indian Hedgehog mRNA in LLC-PK1 tubular cells. These responses were mitigated by siRNA-mediated silencing or pharmacological inhibition of MRTF (CCG-1423) or TAZ (verteporfin). RhoA inhibition exerted similar effects. Unilateral ureteral obstruction, a murine model of mechanically-triggered kidney fibrosis, induced tubular RhoA activation along with overexpression/nuclear accumulation of MRTF and TAZ, and increased transcription of the above-mentioned cytokines. Laser capture microdissection revealed TAZ, TGFβ1 and CTGF induction specifically in the tubular epithelium. CCG-1423 suppressed total renal and tubular expression of these proteins. Thus, MRTF regulates epithelial TAZ expression, and both MRTF and TAZ are critical mediators of PEP-related epithelial cytokine production