The synergistic integration of computational fluid dynamics and experimental fluid dynamics for ground effect aerodynamics studies

This article highlights the ‘synergistic’ use of experimental fluid dynamics (EFD) and computational fluid dynamics (CFD), where the two sets of simulations are performed concurrently and by the same researcher. In particular, examples from the area of ground effect aerodynamics are discussed, where the major facility used was also designed through a combination of CFD and EFD. Three examples are than outlined, to demonstrate the insight that can be obtained from the integration of CFD and EFD studies. The case studies are the study of dimple flow (to enhance aerodynamic performance), the analysis of a Formula-style front wing and wheel, and the study of compressible flow ground effect aerodynamics. In many instances, CFD has been used to not only provide complementary information to an experimental study, but to design the experiments. Laser-based, non-intrusive experimental techniques were used to provide an excellent complement to CFD. The large datasets found from both experimental and numerical simulations have required a new methodology to correlate the information; a new post-processing method has been developed, making use of the kriging and co-kriging estimators, to develop correlations between the often disparate data types

Two-stage directed self-assembly of a cyclic [3]catenane.

Interlocked molecules possess properties and functions that depend upon their intricate connectivity. In addition to the topologically trivial rotaxanes, whose structures may be captured by a planar graph, the topologically non-trivial knots and catenanes represent some of chemistry's most challenging synthetic targets because of the three-dimensional assembly necessary for their construction. Here we report the synthesis of a cyclic [3]catenane, which consists of three mutually interpenetrating rings, via an unusual synthetic route. Five distinct building blocks self-assemble into a heteroleptic triangular framework composed of two joined Fe(II)3L3 circular helicates. Subcomponent exchange then enables specific points in the framework to be linked together to generate the cyclic [3]catenane product. Our method represents an advance both in the intricacy of the metal-templated self-assembly procedure and in the use of selective imine exchange to generate a topologically complex product.This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) and a Marie Curie fellowship for J.J.H. (ITN-2010–264645). The authors thank the Diamond Light Source (UK) for synchrotron beamtime on I19 (MT7984 and MT8464).This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/nchem.220

Mechanical Bonds and Topological Effects in Radical Dimer Stabilization

While mechanical bonding stabilizes tetrathiafulvalene (TTF) radical dimers, the question arises: what role does topology play in catenanes containing TTF units? Here, we report how topology, together with mechanical bonding, in isomeric [3]- and doubly interlocked [2]catenanes controls the formation of TTF radical dimers within their structural frameworks, including a ring-in-ring complex (formed between an organoplatinum square and a {2+2} macrocyclic polyether containing two 1,5-dioxynaphthalene (DNP) and two TTF units) that is topologically isomeric with the doubly interlocked [2]catenane. The separate TTF units in the two {1+1} macrocycles (each containing also one DNP unit) of the isomeric [3]catenane exhibit slightly different redox properties compared with those in the {2+2} macrocycle present in the [2]catenane, while comparison with its topological isomer reveals substantially different redox behavior. Although the stabilities of the mixed-valence (TTF2)^(•+) dimers are similar in the two catenanes, the radical cationic (TTF^(•+))_2 dimer in the [2]catenane occurs only fleetingly compared with its prominent existence in the [3]catenane, while both dimers are absent altogether in the ring-in-ring complex. The electrochemical behavior of these three radically configurable isomers demonstrates that a fundamental relationship exists between topology and redox properties

Discovering privileged topologies of molecular knots with self-assembling models

Despite the several available strategies to build complex supramolecular constructs, only a handful of different molecular knots have been synthesised so far. Here, in response to the quest for further designable topologies, we use Monte Carlo sampling and molecular dynamics simulations, informed by general principles of supramolecular assembly, as a discovery tool for thermodynamically and kinetically accessible knot types made of helical templates. By combining this approach with the exhaustive enumeration of molecular braiding patterns applicable to more general template geometries, we find that only few selected shapes have the closed, symmetric and quasi-planar character typical of synthetic knots. The corresponding collection of admissible topologies is extremely restricted. It covers all known molecular knots but it especially includes a limited set of novel complex ones that have not yet been obtained experimentally, such as 10124 and 15n41185, making them privileged targets for future self-assembling experiments

4'-Chloro-2,2':6',2''-terpyridine

In the title compound, C15H10ClN3, the terpyridine unit adopts a trans,trans conformation. Mol­ecules assemble into [pi]-stacked columns along the b axis, with an inter­planar distance of 3.51 Å

Alignment technique for three-dimensional laser Doppler anemometry

Three-dimensional laser Doppler anemometry is a powerful, non-intrusive measurement technique. The high data rate point measurement allows direct quantification of turbulence quantities. However, for this type of study, a very high level of laser beam alignment is required; without good alignment only mean flow measurements are possible. We report here on an alignment procedure that is simple and cost-effective, yet results in much higher data rates than traditional, pinhole-based methods.5 page(s

Curly-curly, loop-loop : homoleptic metal(ii) complexes of pyridinecarbaldehyde 4'-(2,2':6',2''-terpyridyl)hydrazones and their coordination polymers

The ligands 4-, 3- and 2-pyridinecarbaldehyde 4`-(2,2`:6`,2 ``-terpyridyl)hydrazone (1,2 and 3) have been prepared and characterized. In the homoleptic iron(II) and ruthenium( II) complexes, the nitrogen donor atoms of the pendant pyridine rings subtend an obtuse angle (approximate to 155 degrees) at the metal centre, thus providing an expanded ligand, which can be used for the assembly one-dimensional coordination polymers with an undulating backbone. Protonation of the pendant pyridine rings in [FeL2](2+) (L = 1, 2, 3) or [RuL2](2+) ( L = 1, 2) leads to a colour change from purple to blue, or red to pink, respectively, as the MLCT band shifts to a lower energy. The structural data for [Fe(H-2)(2)][PF6](3)center dot 3.5MeCN center dot 2.5H(2)O (where [H-2](+) is the monoprotonated ligand) show that the [Fe(H2)(2)](3+) cations form one-dimensional chains supported by NpyH center dot center dot center dot N-py hydrogen bonds and that the undulating chains pack to give a porous material, with channels that accommodate the anions and solvent molecules. A single-crystal X-ray diffraction determination of [Fe(NCS)(2)(Ru(1)(2))(2)][Fe-2(NCS)(6)(OEt)(2)(EtOH)(2)][NCS](2) center dot 4EtOH center dot H2O(n) reveals that pairs of [Ru(1)(2)](2+) cations connect Fe(NCS)(2) units to give a one-dimensional polymer comprising of linked metallamacrocycles

Improvement of LDA alignment

Three dimensional Laser Doppler Anemometry is a powerful, non-intrusive measurement technique. The high date rate point measurement allows direct quantification of turbulence quantities. However, for this type of study, a very high level of laser beam alignment is required; without good alignment only mean flow measurements are possible. We report here on an alignment procedure that is simple and cost-effective, yet results in much higher data-rates than traditional, pinhole-based methods.4 page(s