The Multi-Advective Water Mixing Approach for Transport through Heterogeneous Media

Finding a numerical method to model solute transport in porous media with high heterogeneity is crucial, especially when chemical reactions are involved. The phase space formulation termed the multi-advective water mixing approach (MAWMA) was proposed to address this issue. The water parcel method (WP) may be obtained by discretizing MAWMA in space, time, and velocity. WP needs two transition matrices of velocity to reproduce advection (Markovian in space) and mixing (Markovian in time), separately. The matrices express the transition probability of water instead of individual solute concentration. This entails a change in concept, since the entire transport phenomenon is defined by the water phase. Concentration is reduced to a chemical attribute. The water transition matrix is obtained and is demonstrated to be constant in time. Moreover, the WP method is compared with the classic random walk method (RW) in a high heterogeneous domain. Results show that the WP adequately reproduces advection and dispersion, but overestimates mixing because mixing is a sub-velocity phase process. The WP method must, therefore, be extended to take into account incomplete mixing within velocity classes.

Ceilometers as planetary boundary layer height detectors and a corrective tool for COSMO and IFS models

The significance of planetary boundary layer (PBL) height detection is apparent in various fields, especially in air pollution dispersion assessments. Numerical weather models produce a high spatial and temporal resolution of PBL heights; however, their performance requires validation. This necessity is addressed here by an array of eight ceilometers; a radiosonde; and two models – the Integrated Forecast System (IFS) global model and COnsortium for Small-scale MOdeling (COSMO) regional model. The ceilometers were analyzed with the wavelet covariance transform method, and the radiosonde and models with the parcel method and the bulk Richardson method. Good agreement for PBL height was found between the ceilometer and the adjacent Bet Dagan radiosonde (33 m a.s.l.) at 11:00 UTC launching time (N=91 d, ME =4 m, RMSE =143 m, R=0.83). The models' estimations were then compared to the ceilometers' results in an additional five diverse regions where only ceilometers operate. A correction tool was established based on the altitude (h) and distance from shoreline (d) of eight ceilometer sites in various climate regions, from the shoreline of Tel Aviv (h=5 m a.s.l., d=0.05 km) to eastern elevated Jerusalem (h=830 m a.s.l., d=53 km) and southern arid Hazerim (h=200 m a.s.l., d=44 km). The tool examined the COSMO PBL height approximations based on the parcel method. Results from a 14 August 2015 case study, between 09:00 and 14:00 UTC, showed the tool decreased the PBL height at the shoreline and in the inner strip of Israel by ∼100 m and increased the elevated sites of Jerusalem and Hazerim up to ∼400 m, and ∼600 m, respectively. Cross-validation revealed good results without Bet Dagan. However, without measurements from Jerusalem, the tool underestimated Jerusalem's PBL height by up to ∼600 m.

Estimations of the Mexicali Valley (Mexico) Mixing Height

We report estimations of the Mexicali Valley (Mexico) mixing height for three seasons. Surface and upper air meteorological measurements were carried out nearby Cerro Prieto geothermal power plant during July 2010 (summer), January 2012 (winter), and October 2016 (autumn). Four different methods were applied to estimate the convective boundary layer (CBL) height from radiosonde (RS) profiles: the parcel method, the gradients method, the least-squares variational approach based on the slab model of the CBL structure, and a covariance method. For nocturnal conditions, we used diagnostic models based on friction velocity and Monin–Obukhov length. Under unstable conditions, we obtained (on average) mixing heights of 497 m at 06:00 LST, 1242 m at 12:00 LST, 1404 m at 15:00 LST, and 482 at 18:00 LST during summer; 754 m at 12:00 LST during winter; and 1195 m at 12:00 LST and 13:00 m between the 14:00 and 15:00 LST during the autumn. The results allowed adjusting a semiempirical model to evaluate mixing height from turbulent sensible heat flux and friction velocity data. Our results provide practical tools that could facilitate the application of regulatory dispersion models to assess air quality in the region.

Ceilometers as planetary boundary layer detectors and a corrective tool for ECMWF and COSMO NWP models

The growing importance of the planetary boundary layer (PBL) height detection is apparent in various fields, from air pollution analysis to weather prediction. In recent years micro-lidars such as ceilometers have been recognized as an efficient tool for such measurements. Here, the daytime summer PBL height is measured by eight ceilometers throughout Israel, along with with radiosonde profiles, the global IFS model, and the regional COSMO model. The analysis focused on three PBL height evaluation methods: the bulk Richardson method, the parcel method, and the wavelet covariance transform method. The best agreement between the PBL heights derived from a single radiosonde site on 33 summer days was found by the adjacent ceilometer (mean error = 12 m, RMSE = 97 m). Spatial analysis of the PBL heights derived from the models on 13 days in reference to five ceilometer measurement sites revealed COSMO evaluations by the bulk Richardson method (COSMOR) produced the best results for both flat (mean error = 19 m, RMSE = 203 m) and elevated terrain (mean error = −6 m, RMSE = 251 m). To improve COSMOR results, a regression tool was assimilated based on the PBL height difference between COSMOR and ceilometers. The regression is based on the altitude and distance from the shoreline for eight ceilometer sites.

Sensitivity to herbicides of two spring forage pea cultivars

An important element of spring pea growing technology is weed control as the crop is highly sensitive to them, especially in the early stages of its development. The use of various herbicide preparations with a diverse mechanism and spectrum of action, changes in weed associations under the influence of various factors, as well as the selection of new varieties necessitates a constant study of the problem of the efficacy of herbicide preparations and the sensitivity of varieties to them. The aim of the present study was to investigate the sensitivity of two cultivars of spring forage pea to different herbicide preparations. During the period 2006-2008 in the village of Lyubenova mahala, Stara Zagora region, a three-factor field experiment was conducted by the fractional parcel method in four replications and size of the harvest plot 10m2. Factor A includes cultivars of spring peas, factor B – herbicide variants, factor C – doses of herbicides. It has been proven that the plants of both varieties, Pickardi and Amitie, are killed by 2.4 D, both in single and double dose. The highest average plant height was recorded in the Amitie cultivar treated with Basagran 600 SL herbicide at the double dose (3.0 L/ha). The highest were the values of the parameter number of beans per plant obtained in the Amitie cultivar treated with Basagran 600 SL and Pivot 100 SL – 0.8 L/ha, in the soil. A statistically proven highest average value of the parameter seed mass per plant was obtained in the Amitie variety treated with the Basagran 600 SL herbicide (12.667g) and the lowest – in Pickardi with the herbicide Pivot (10.330g).

A study of the controlling parameters of fuel air mixture formation for ECN Spray A

Designing future ultra-high efficiency, ultra-low emission engines requires an in depth understanding of the multiscale,multi-phase phenomena taking place in the combustion chamber. The performance of the fuel deliverysystem is key in the air fuel mixture formation and hence the combustion characteristics, however in most spraymodelling approaches is not considered directly. Thus, it is important to understand how the selection of modelsthat mimic injection process affect predictions. In this paper we present an Eulerian-Lagrangian framework basedon OpenFOAM libraries to model spray injection dynamics. The framework accounts for primary droplet formation(based on a parcel method with predefined initial droplet size distribution), secondary droplet breakup, evaporationand heat transfer. In order to account for the interaction of droplets with turbulence, simulations were performedwithin the LES context with two different turbulence models. A systematic variation of the key injection parameters(parcel number, parcel size distribution) of the parcel method as well as the grid size was considered. Varying theparcel number affects the initial droplet size distribution which in turn, depending on the selection of the turbulenceand the evaporation sub-models, affects: spray dispersion; spray penetration; and subsequent droplet size distribution.Results were validated against the baseline experimental data for evaporating ECN Spray A with n-dodecanechosen as a surrogate for Diesel fuel.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4703