27 research outputs found
Compressive properties of min-mod-type limiters in modelling shockwave-containing flows
The long-ignored compressive properties of Min-mod-type limiter is investigated in this manuscript by demonstrating its potential in numerically modelling shockwave-containing flows, especially in shock wave/boundary layer interaction (SWBLI) problems. Theoretical studies were firstly performed based on Sweby’s total variation diminishing (TVD) limiter region and Spekreijse’s monotonicity-preserving limiter region to indicate Min-mod-type limiters’ compressive properties. The influence of limiters on the solution accuracy was evaluated using a hybrid-order analysis method based on the grid-independent study in three typical shockwave-containing flows. The conclusions are that, Min-mod-type limiter can be utilized as a dissipative and/or compressive limiter, but depending on the reasonable value of the compression parameter. The compressive Min-mod limiter tends to be more attractive in modelling shockwave-containing flows as compared to other commonly preferred limiters because of its stable computational process and its high-resolution predictions. However, the compressive Min-mod limiter may suffer from its slightly poor convergence, as that observed in other commonly accepted smooth limiters in modelling SWBLI problems. © 2020, The Author(s)
Comparative morphology of the forewing base articulationin Sternorrhyncha compared with a representative of Fulgoromorpha (Insecta, Hemiptera)
The forewing articulation of single species
from each of the four subgroups of Sternorrhyncha
(Aleyrodomorpha, Aphidomorpha, Coccomorpha, Psyllomorpha)
was examined by optical and scanning electron
microscopy. The species were compared with a species of
Cixiidae (Fulgoromorpha), as an outgroup of Sternorrhyncha.
We present the results of a comparative analysis
of the forewing articulation in these five groups, propose a
standardized terminology and compare our findings with
those previously reported. The wing base of all examined
species is composed of the following structures: anterior
and posterior notal wing process, first, second, and third
axillary sclerites, tegula, and axillary cord. The number of
elements included in the wing base and the surrounding
area is the greatest in Cacopsylla mali, the most complicated
species from Sternorrhyncha. Based on the shape of
axillary sclerites and the number of elements forming the
wing base environment, Orthezia urticae (Coccomorpha)
and Cixius nervosus (Fulgoromorpha) are the most similar.
Among Sternorrhyncha, the most similar axillaries are
those of Aphis fabae and Orthezia urticae, which is congruent
with existing classifications. In this paper we show
that the four groups from Sternorrhyncha exhibit their own
distinct wing base morphology