Search

There was an omission in the original publication [1]. The authors showed SOTR values in a figure but did not mention how these values were calculated. As a consequence, the calculations based upon the SOTR also need to be more specific, which is why “the twisted regime of” has been added in front of “the hyperbolic funnel”. An addition has been made to the paper as Supplementary Information where this information has been added, Section 3, Paragraph 5: Figure 4 shows KLa and SOTR values (see Supplementary Information for details) dependent also as a function of flow rate. Average KLa values (for 20 °C) for air jet, impellers and paddle aerators [12] are shown for comparison. The plot shows that the KLa values obtained with the free surface vortex in a hyperbolically shaped funnel are considerably higher than those of the three commercial systems used for comparison, especially in the twisted regime. These high oxygen transfer rates are a consequence of the aforementioned combination of high area-to-volume ratios and possibly enhanced turbulence close to the interface. On the other hand, the SOTR values (up to 0.5 kg/h) [12] are comparable to air jet system and lower than those reported for impeller and paddle systems (between 1.0 and 2.5 kg/h) [12]. This is due to the short hydraulic retention times in the hyperbolic funnel (typically less than a minute). A possibility to increase the SOTR value is the application of a cascade of funnels which would multiply the HRT with a factor representing the number of funnels, whilst maintaining the desired flow regime and thus the KLa value. For practical applications the specific energy demand of such a cascade can be estimated as follows: The twisted regime of the hyperbolic funnel tested in this work has a specific energy demand of 0.01 kWh/kg O2 (see Appendix A for calculation details). In comparison, the specific energy demands of mechanical aerators range from 0.42 to 0.83 kWh/kg O2 [13] and the specific energy demands

There was an omission in the original publication [1]. The authors showed SOTR values in a figure but did not mention how these values were calculated. As a consequence, the calculations based upon the SOTR also need to be more specific, which is why “the twisted regime of” has been added in front of “the hyperbolic funnel”. An addition has been made to the paper as Supplementary Information where this information has been added, Section 3, Paragraph 5: Figure 4 shows KLa and SOTR values (see Supplementary Information for details) dependent also as a function of flow rate. Average KLa values (for 20 °C) for air jet, impellers and paddle aerators [12] are shown for comparison. The plot shows that the KLa values obtained with the free surface vortex in a hyperbolically shaped funnel are considerably higher than those of the three commercial systems used for comparison, especially in the twisted regime. These high oxygen transfer rates are a consequence of the aforementioned combination of high area-to-volume ratios and possibly enhanced turbulence close to the interface. On the other hand, the SOTR values (up to 0.5 kg/h) [12] are comparable to air jet system and lower than those reported for impeller and paddle systems (between 1.0 and 2.5 kg/h) [12]. This is due to the short hydraulic retention times in the hyperbolic funnel (typically less than a minute). A possibility to increase the SOTR value is the application of a cascade of funnels which would multiply the HRT with a factor representing the number of funnels, whilst maintaining the desired flow regime and thus the KLa value. For practical applications the specific energy demand of such a cascade can be estimated as follows: The twisted regime of the hyperbolic funnel tested in this work has a specific energy demand of 0.01 kWh/kg O2 (see Appendix A for calculation details). In comparison, the specific energy demands of mechanical aerators range from 0., Energy Technology

Aeration is one of the most cost intensive steps in water and wastewater treatment due to the large energy requirement for the creation of large surfaces for sufficient gas exchange as well as for providing efficient liquid transport in order to exchange saturated liquid elements at the surface with unsaturated ones from the bulk. In this work we show that geometrically constrained vortices in a hyperbolic funnel are a promising aeration technique as they meet these criteria and allow oxygen transfer coefficients up to 50 h−1, a number significantly higher than that of comparable methods like air jets or impellers (<10 h−1)., Energy Technology

Lucerne (Medicago sativa L.) is a perennial legume with high importance as fodder crop under organic farming. Our study analyzes biomass growth and influence on soil water dynamics of three lucerne cultivars in a field experiment and using the simulation model CropSyst. The objective was to evaluate the model for a perennial legume crop, study the relation of cultivar traits with soil water relations and derive a lucerne ideotype for temperate, semi-arid conditions. Two cultivars of European origin (Sitel and Niva)were compared to an Iranian one (Mohajeran). Measurements were made under irrigated (non-water limited) and rain-fed (water limited) conditions. Sitel achieved a cumulative biomass (dry matter yield)of 36.8 t ha−1 (irrigated) and 25.3 t ha−1 (rain-fed) over six cuts during the two experimental years, being significantly higher compared to the other cultivars. It was depicted that for Sitel and Mohajeran biomass growth was determined by the ratio of rainfall-to-evapotranspiration. Niva on the contrary exhibited a distinct response of biomass growth to profile water content changes. Also the more even root distribution over the soil profile of Niva indicated an efficient water uptake for this cultivar. CropSyst simulated biomass growth (RMSE 0.58–3.52 t ha−1) and water content in the soil profile (RMSE 20.9–50.6 mm) satisfactorily. Indices of agreement revealed a better model performance for irrigated conditions compared to water-limited growth. Model deviations from measured biomass and profile water content were highest for Mohajeran and it can be attributed to an inadequate distribution of root water extraction over the soil profile in relation to rooting density. Scenario analysis revealed that for the temperate, semi-arid conditions at the site, a maximum root depth between 1.3 and 1.8 m is sufficient for optimum growth and water use. Optimization of growth is largely determined by leaf traits such as specific leaf area, but our analysis depicted that i