Oscillating airfoils and their wake

The unsteady phenomena in the wake of an oscillating wing or rotor blade are examined theoretically using the Prandtl approximation of the vortex-transport equation. A mathematical model is developed and applied to such problems as the effect of winglets on the performance of fixed wings and the possibly of employing similar designs in rotor blades. Model predictions for several profiles are compared with published and experimental measurements, and good agreement is found. Graphs and diagrams are provided

Analysis of in-situ observations in the Strait of Gibraltar

During the EU-project CANIGO intensive ship-board observations were carried out in April 1996 and October 1997 in order to observe the spatial and temporal variability of the flow, of the internal bore and of the water mass structure in the Strait of Gibraltar. An inverse model for the current and interfacefluctuations was developed to remove tidal currents from the measurement and to calculate the volume transport for the in and outflow seperately. In addition traveltime measurements across the strait have been analysed to test the suitability of acoustical instruments for a longterm monitoring of the exchange through the strait

Intercomparing drifts from eddy-resolving and cycling floats in the deep western boundary current along the Mid-Atlanic Ridge

The Lagrangian nature of cycling floats is evaluated in the framework defined by the Deep Western Boundary Current of the Mid-Atlantic Ridge. In a statistical approach, speeds and drifts are estimated for an APEX cycling float and compared with the velocities inferred from a park ensemble of four eddy-resolving RAFOS floats. They were deployed at the same location and ballasted for drifting at the same mission depth. Displacement errors induced by geostrophic shear and wind forced currents are analyzed. We observe that the velocity estimated from the RAFOS floats is not statistically different from the velocity estimated from the APEX float. Likewise, the initial separation between the cycling float and a simultaneously deployed RAFOS float has been studied in terms of the turbulent diffusivity. Though the performance of this study in comparable cases without a mean current field may be limited, these oceanic observations support exploiting the Lagrangian nature of the cycling floats

Accuracy of current profile measurements: Effect of tropical and midlatitude internal waves

The effect of midlatitude and tropical internal wave variability on current profile measurements is investigated and quantified to yield practical error estimates. First, a data set of Pegasus current profiles from the tropical Atlantic (6°S to 6°N) is analyzed for their rms down/up differences, which are compared with predictions from Garrett‐Munk type internal wave theory and with statistics derived from current meter moorings in the same region. The agreement in terms of amplitudes and vertical distribution proves that most of those differences are due to internal waves and not instrumental errors. Nonetheless, this is the noise of the measurements, if low‐frequency motions are sought, and the errors can thus be quantified using the same internal wave theories. At midlatitudes the error variance is the usual 44(N/3 cph) cm2/s2 with some latitude dependence, and the effect of averaging in the vertical or summing several profiles (e.g., up and down) is estimated. The same is done for equatorial situations, where construction of a crude equatorial frequency spectrum for internal waves yields 77(N/3 cph)cm2/s2 for the error variance. Again, error reduction due to averaging is estimated

Climate Changes Disputes at the World Trade Organization: National Energy Policies and International Trade Liability

This Article draws attention to the different outcomes that may result when WTO law is applied to resolve climate related national energy policy disputes, signals this might send for national energy policies, and how a subtle effect of indirect state liability may arise. Several pending or unresolved complaints currently at the WTO are used to demonstrate these effects. The complaints include the greenhouse gas controversy, the wind energy subsidies complaint, and the feed-in tariffs complaint. The next section, Section II, presents the basic WTO obligations of the four countries involved in these complaints (Japan, Canada, USA, China), and ways that state liability can theoretically arise. Section III explains, with some example cases, how the consistency of national environmental policies with WTO laws has previously been decided. Section IV explains the main energy-related obligations of the countries under the international climate change regime. Section V discusses those unresolved complaints in light of the countries’ WTO and climate regime obligations. Finally, the article concludes by demonstrating that the WTO not only has the power to change the direction of countries’ energy policies, but its decisions may also lead to indirect state liability. It should be noted that this paper is not about the compatibility of national energy policies with WTO law per se. Therefore there is no exhaustive discussion of all analogous environmental compatibility cases. Select cases are discussed only as indicators of WTO’s potential to change national (energy) policies as well as to lead to a subtle and indirect effect on state liability

Transport estimates in the Strait of Gibraltar with a tidal inverse model

To estimate the volume transport through the Strait of Gibraltar and to study the spatial structure of the time-variable flow, a varying number of current meter moorings were maintained at the eastern entrance of the strait between October 1994 and April 1998, and was complemented with intensive shipboard measurements during the European Union project Canary Island Azores Gibraltar Experiment (CANIGO). A tidal inverse model is used to merge these data sets in order to investigate the flow at the eastern entrance of the strait. The two-dimensional structure of the tidal flow was described by simple analytical functions. Harmonics with the seven most important tidal frequencies were used as temporal functions. With this model, the tidal currents can be predicted for any time and location at the eastern entrance of the strait, and more than 92% of the variance of the lower layer flow is explained. It was used to remove the tidal currents from the individual measurements and to calculate the mean flow through the strait from the residuals. Combined with a similar inverse model for determining the depth of the interface between Mediterranean and Atlantic water, the volume transport was estimated to be 0.81 ± 0.07 Sv for the upper layer and −0.76 ± 0.07 Sv for the lower layer. The correlation of the tidal currents and the fluctuations of the interface accounts for ∼7% of the transport at the eastern entrance

Lessons Learned from Establishing the Energy-Informatics Business Model: Case of a German Energy Company

Energy and utilities companies find themselves in a paradoxical situation in which their traditional business models are losing profitability, and they must advocate energy efficiency and climate-protection goals, and thus encourage their customers to save energy. As a result, they must partially cannibalize their business models and experiment with new models and techniques. Energy Informatics (EI) offers promising business opportunities that alleviate the concerns of energy companies about traditional revenue streams. However, recent discussions on this issue lack proof of concept and success determinants. This business case study fills this gap by describing the journey of German energy company Energiequelle, which established a sustainable business model based on EI. On the basis of our interview data, we analyzed Energiequelle’s EI strategy and stakeholder management and present six lessons learned. We believe that our practice-oriented research provides profound insight, especially to high-level executives and policymakers.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli